U.S. patent application number 12/256814 was filed with the patent office on 2010-01-14 for pressure-sensitive adhesives and process for preparing them.
This patent application is currently assigned to tesa AG. Invention is credited to Thilo Dollase, Alexander Prenzel.
Application Number | 20100010170 12/256814 |
Document ID | / |
Family ID | 41231038 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100010170 |
Kind Code |
A1 |
Prenzel; Alexander ; et
al. |
January 14, 2010 |
PRESSURE-SENSITIVE ADHESIVES AND PROCESS FOR PREPARING THEM
Abstract
The invention relates to a process for preparing a
pressure-sensitive adhesive based on at least one polymer, in the
course of which said at least one polymer is crosslinked, the
polymer having functional groups Y and having been admixed,
further, with at least one kind of functionalized particles which
have at least one nonpolymeric base unit, wherein the particles
having a surface modification of the base unit, the surface
modification of the particles having at least one kind of
functional groups Z, which can not undergo any reaction with the
functional group Y and is converted into group X by thermal energy,
electromagnetic radiation, particulate radiation and/or sound
energy and the crosslinking of the polymer being brought about at
least in part by a reaction of the functional groups X of the
particles and the functional groups Y of the polymer, and further
to pressure-sensitive adhesives based on at least one crosslinked
polymer component, the crosslinking of the polymer component being
brought about at least in part by incorporation of the
functionalized particles, the particles having at least one
nonpolymeric base unit and also a surface modification of this base
unit, and the surface modification of the particles having at least
one kind of functional groups Z which, after conversion to group X
by way of thermal energy, electromagnetic radiation, particulate
radiation and/or sound energy, are capable of reacting with
functional groups Y present in the polymer component, and also to
the use of surface-modified functionalized particles having a
nonpolymeric base unit as crosslinking reagents for crosslinking
polymers for preparing pressure-sensitive adhesives.
Inventors: |
Prenzel; Alexander;
(Hamburg, DE) ; Dollase; Thilo; (Hamburg,
DE) |
Correspondence
Address: |
GERSTENZANG, WILLIAM C.
875 THIRD AVE, 8TH FLOOR
NEW YORK
NY
10022
US
|
Assignee: |
tesa AG
Hamburg
DE
|
Family ID: |
41231038 |
Appl. No.: |
12/256814 |
Filed: |
October 23, 2008 |
Current U.S.
Class: |
525/451 |
Current CPC
Class: |
C09J 201/02 20130101;
C08K 9/06 20130101 |
Class at
Publication: |
525/451 |
International
Class: |
C09J 133/08 20060101
C09J133/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2008 |
DE |
10 2008 032 570.8 |
Claims
1. A process for preparing a pressure-sensitive adhesive comprising
the crosslinking product of at least one polymer and at least one
kind of functionalized particles, the polymer having reactive
centres, the functionalized particles having at least one
nonpolymeric base unit; the nonpolymeric base unit having a surface
modification, the surface modification of the nonpolymeric base
unit having at least one kind of functional groups Z which under
the conditions during the preparation and processing of the polymer
and/or of the noncrosslinked pressure-sensitive adhesive do not
enter into any reaction with the reactive centres of the polymer,
wherein the process comprises the following steps: converting at
least some of the functional groups Z of the particles, by supply
of energy, overcoming the activation energy of conversion, into
functional groups X which are capable, under appropriate process
conditions, of entering into a reaction with the reactive centres
of the polymer, forming the crosslinking product, comprising
reacting the functional groups X of the particles with the reactive
centres of the polymer under appropriate process conditions.
2. Process according to claim 1, wherein the functionalized
particles, on the same or further nonpolymeric base units,
additionally have functional groups X.sub.a, and, in the process,
optionally before the conversion of the groups Z into the groups X,
a crosslinking step takes place which comprises reaction of the
functional groups X.sub.a with the reactive centres of the
polymer.
3. Process according to claim 1, wherein the supplied energy is
thermal energy, electromagnetic radiation, particulate radiation
and/or sound energy.
4. Process according to claim 1, wherein the reactive centres of
the polymer are functional groups Y.
5. Process according to claim 1, wherein the functionalized
particles are in the form of a dispersion in water and/or organic
solvents.
6. Process according to claim 1, wherein the functionalized
particles used are metal oxides and/or semimetal oxides, salts of
alkaline earth metals, or silicate-based minerals.
7. Process according to claim 1, wherein the functionalized
particles are spherical, rodlet-shaped and/or platelet-shaped
particles and/or aggregates thereof.
8. Process according to claim 1, wherein the particles are
nanoscale in at least one of their spatial dimensions.
9. Process according to claim 1, wherein the functionalized
particles used are aggregates of spherical primary particles, in
which all three spatial dimensions occupy in each case an extent of
not more than 100 nm.
10. Process according to claim 1, wherein the functionalized
particles are used in a concentration range of 0.1% to 15% by
weight, based on the polymer.
11. Process according to claim 1, wherein the conversion of the
functional groups Z into the functional groups X and the reaction
with the reactive centres of the polymer take place
simultaneously.
12. Process according to any claim 1, wherein the conversion of the
groups Z into the groups X entails removal of protective groups or
deblocking.
13. Pressure-sensitive adhesive obtained by the process of claim
1.
14. Pressure-sensitive adhesive based on at least one crosslinked
polymer component, the crosslinking of the polymer component being
brought about at least in part through the incorporation of
functionalized particles, the particles prior to Incorporation
having at least one nonpolymeric base unit which is at least partly
surface-modified in such a way that it possesses one kind of
functional groups Z, the groups Z, following conversion by means of
energy supply into groups X, being capable of reacting with
reactive centres of the polymer that are present in the polymer
component.
15. Polymer mixture comprising at least one polymer and at least
one kind of functionalized particles, the polymer having reactive
centres comprising functional groups Y, the functionalized
particles having at least one nonpolymeric base unit; the
nonpolymeric base unit having a surface modification, the surface
modification of the nonpolymeric base unit having at least one kind
of functional groups Z which under the conditions during the
preparation and processing of the polymer and/or of the
noncrosslinked pressure-sensitive adhesive do not enter into any
reaction with the reactive centres of the polymer, the functional
groups Z being convertible, by energy supply, overcoming the
activation energy of conversion, into functional groups X which are
capable under appropriate process conditions of entering into a
reaction with the reactive centres of the polymer.
16. (canceled)
17. The process of claim 6, wherein said functionalized particles
are clay minerals or clays.
Description
[0001] The present invention relates to pressure-sensitive
adhesives which preferentially can be processed without solvent and
are distinguished not only by good processing properties and, in
particular, coatability but also by good product properties. The
invention embraces the composition of innovative pressure-sensitive
adhesive formulations and also their preparation, processing, and
use in self-adhesive products. Also part of this invention is an
innovative scheme allowing the combination of good processing
properties and good product properties to be realized for
pressure-sensitive adhesive formulations of this kind.
BACKGROUND OF THE INVENTION
[0002] Within the field of adhesives, pressure-sensitive adhesives
(PSAs) are notable in particular for their permanent tack. A
material which has permanent tack must at any given point in time
have an appropriate combination of adhesive and cohesive
properties. This distinguishes it, for example, from reactive
adhesives, which in the unreacted state offer virtually no
cohesion. For good product properties it is appropriate to adjust
PSAs in such a way that the balance of adhesive and cohesive
properties is at an optimum. This balance is typically achieved by
converting polymer chains present in PSA formulations into
wide-meshed networks. The nature of this network has a critical
influence on the adhesive and cohesive properties of the PSA. A
material featuring pronounced crosslinking, although having good
cohesion, nevertheless has reduced pliancy, so that the material is
unable to adapt adequately to the roughness of a substrate surface.
Moreover, a material featuring pronounced crosslinking has only a
relatively low ability to dissipate deformation energy such as
occurs under load. Both phenomena reduce the bond strength. A
material with a low level of crosslinking, in contrast, although
able to flow on rough surfaces and to dissipate deformation energy,
with the consequence that the adhesion requirements may be met, is
nevertheless inadequate in its resistance to load, owing to a
reduced cohesion.
[0003] One kind of crosslinking which has an effect on the
adhesion/cohesion balance is temporary polymer-chain interlooping.
However, this is sufficient for adequate cohesion of the PSA only
when the molar mass of the polymers is sufficiently high. PSAs
based on natural rubbers may rest solely on this crosslinking
principle. Further possibilities of setting the crosslinking of the
PSA are chemical crosslinks, which are therefore irreversible.
Chemical crosslinking can also be achieved by means of radiation
treatment of the PSAs. Another possibility is to utilize physical
crosslinking principles. Examples of such crosslinks, typically
thermoreversible, in PSAs are present in thermoplastic elastomers,
such as in certain block copolymers or semicrystalline
polymers.
[0004] Besides the crosslinking principles referred to, it is also
possible to use fillers for raising the cohesion. In that case a
combination of filler/filler interactions and filler/polymer
interactions frequently leads to the desired reinforcement of the
polymer matrix. A raising of cohesion based thereon represents a
further physical crosslinking variety.
[0005] For fillers which are mentioned with a view to a reinforcing
effect in PSAs, the class of the pyrogenic (or fumed) silicas
deserves particular mention. These silicas are used, inter alia, as
thickeners, gelling agents or thixotropic agents in a very wide
variety of fluids, utilizing their effect on the rheological
properties of the fluids. The use of hydrophilic and of hydrophobic
silica is described in this context. Examples of the use of
pyrogenic silica in the field of PSAs are described in US
20060205835 by tesa AG, in U.S. Pat. No. 4,710,536 by 3M and in EP
108 32 04 B1 by Dow Corning.
[0006] As further fillers, the use of modified phyllosilicates for
improving product properties has been described in U.S. Pat. No.
7,144,928 by tesa AG, in WO 02/24756 A2 by Rohm & Haas and in
JP 2002 167, 557 by Sekisui.
[0007] In all of these cases the reinforcement results from the
effect of the particles on the elasticity modulus of the elastomer
composite. The interaction in this case is brought about by
physical interactions between individual particles, on the one
hand, and between particles and polymers, on the other. Often,
however, these physical interactions are not enough to withstand
even low mechanical deformations, such as may occur, for example,
when a PSA joint is loaded by shearing or peeling. This nonlinear
phenomenon is known as the Payne effect and is manifested as a loss
of elasticity modulus under deformation. A review of the
description of this effect and of various approaches as a
mechanistic explanation is given by Heinrich and Kluppel [G.
Heinrich, M. Kluppel, Adv. Polym. Sci., 2002, 160, 1-44].
[0008] In the preceding section, a variety of examples have been
given of types of crosslinking that may be employed in PSAs for
improving the product properties, especially the cohesion. For each
of these varieties of crosslinking, the question arises of to what
extent they affect the processing properties, and more particularly
the coating characteristics. This is debated below.
[0009] Besides the product properties and hence the optimum balance
of adhesive and cohesive properties in a PSA, its processing
properties are also of central importance. Generally speaking, the
processing properties of a formulation are reduced by its
crosslinking. In a majority of cases indeed, processing becomes
impossible. It is therefore advantageous to carry out or to
initiate crosslinking not until during or after processing, and in
particular during or after coating. However, where the crosslinking
state results from the mere presence of a constituent in the
formulation, as is the case with the abovementioned fillers, then
the processing characteristics are adversely affected by its very
presence. Polymers with high molar masses are likewise among
formulation constituents which by virtue of their state of
interlooping have advantageous product properties and yet, likewise
owing to their state of interlooping, may show disadvantages in
processing properties. In both cases, namely both interlooping and
fillers, the physical principles which lead to the crosslinking of
the PSA system and hence to advantageous product properties have
negative consequences for the processing characteristics,
particularly the coatability.
[0010] Traditional approaches to escaping this dilemma have been
based on the use of solvents as operating assistants. An increased
environmental awareness and the desire for ever more efficient
production techniques, however, are underlying the trend toward
solvent-free operations. In comparison to solvent processing
methods, the polymer-based PSA base compositions, in the case of
the hotmelt processes have a state of crosslinking in their melt,
as a result of the interlooping and/or filler particles, which is
associated with significantly higher viscosities and
elasticities.
[0011] In contrast to physical modes of crosslinking, chemical
crosslinking methods afford the formation of a network which can be
initiated by an appropriate operating regime only during
processing. However, the use of chemical crosslinkers is limited by
their pot-life reactivity. If the network forms in too pronounced a
way before the material has been coated, the elasticity increase
which has already taken place results in a deterioration in the
processing properties, and reduced-quality coating outcomes may
result. One particular difficulty arises in the case of
solvent-free systems, since, here, elevated temperatures are
necessary for processing, leading at the same time to an
acceleration of the chemical crosslinking reaction. One example of
a system of this kind is described in US 20050129936 A1 by tesa AG.
Radiation crosslinking methods appear advantageous in this context,
since only after coating is the formation of a network initiated
deliberately, as proposed for example in EP 153 21 82 A1 by tesa AG
and EP 167 68 70 A1 by National Starch. However, in order to obtain
networks having a structure satisfying the subsequent product
requirements in respect of shear strength, polymers of decidedly
high molar mass are needed, which in turn, as a result of their
state of interlooping, may have disadvantages in terms of
processing characteristics.
[0012] Typically, the processing properties of a material
deteriorate as its elasticity goes up. Formation of a network
always leads to an increase in the storage modulus and hence to
upper elasticity. Consequently, there is a deterioration in the
fluidity, which is needed for processing of the coating, or even a
complete loss of fluidity. In the case of coating, then,
inhomogeneities may occur in the coating outcome, possibly going as
far as melt fracture. A variety of authors describe this phenomena,
especially for capillary dies and extrusion dies. Literature
references on this can be found in Pahl et al. [M. Pahl, W.
Glei.beta.le, H.-M. Laun, Praktische Rheologie der Kunststoffe und
Elastomere, 4th ed., 1995, VDI Verlag, Dusseldorf, p. 191f] and
Tanner [R. I. Tanner, Engineering Rheology, 2nd ed., 2000, Oxford
University Press, Oxford, p. 523f].
[0013] Systems are therefore sought which preferably can be coated
without solvent and which exhibit a combination of good product
properties on the one hand--and here particularly in respect of
cohesion--and improved processing properties on the other,
especially coatability.
[0014] One particularly advantageous example of systems which at
least partly satisfy this combination of requirements is
represented by block copolymers comprising segments which soften at
high temperatures (known as the hard phase) and others which at
application temperature are present in melted form. The softening
temperature of the hard phase is typically adjusted, through the
use of specific monomers, such that good product properties prevail
at room temperature and yet at temperatures that are rational from
an operational standpoint the material can easily be coated from
the melt. Since these materials typically do not have high molar
masses, their melt viscosity and elasticity, as soon as the hard
phase is in softened form, are comparatively low.
[0015] A disadvantage of the above-discussed PSAs based on block
copolymers, however, is their thermal shear strength, which is
limited by the softening of the hard domains that sets in at an
elevated temperature. A further disadvantage to be cited are the
costly and inconvenient preparation conditions for block
copolymers. In order to be able to prepare polymers having the
requisite blocklike structure in sufficient quality, controlled or
living polymerization techniques are necessary, some of which are
complex. Moreover, not all monomer combinations can always be
easily realized. Hence the block copolymer approach, on the one
hand, therefore, is seen as not being universally flexible for
numerous polymer systems. On the other hand there is a need for
PSAs having better thermal shear strength.
[0016] Surface-functionalized fillers, more particularly the
classes of the fumed and precipitated silicas, are likewise
described in US 2006/0035087 A1 of NanoProducts Corp., US
2006/0204528 A1 of Byk-Chemie GmbH, and WO 2007/024838 of E. I. du
Pont de Nemours and Co., in order to construct a chemical network.
Crosslinking in those cases takes place through formation of
covalent bonds, the crosslinking reactions being initiated
thermally. This in turn may be problematic when the fillers are
incorporated, and when the composites are processed, since, owing
to elevated temperatures, crosslinking may commence during the
actual operation. DE 10 2005 022 782 A1 of tesa AG describes
functionalized particles which, on exposure to electromagnetic
radiation and/or particulate radiation, lead to crosslinking of the
pressure-sensitive adhesive; however, there continues to be a need
for thermally initiable crosslinking methods for pressure-sensitive
adhesives which can nevertheless be processed in a hotmelt
process.
[0017] It is therefore an objective of the present invention to
provide a flexible scheme which encompasses a suitable combination
of material and process so that it is possible to prepare PSAs
which can preferably be processed without solvent and which have
good processing properties, such as, for example, an increased pot
life for the crosslinking reaction, and good product
properties.
SUMMARY OF THE INVENTION
[0018] As has now been found, this combination of requirements,
consisting of good processing properties and good product
properties, can be obtained by preparing crosslinked PSAs using a
process in which a specific PSA formulation comprises particles
with blocked and/or deactivated functionalities, said particles
being functionalized in such a way that, during or after the
coating operation, the particles can be linked to at least one kind
of polymeric constituents of the PSA formulation by exposure to, in
particular, thermal energy and/or radiation energy, in particular
to electromagnetic radiation or particulate radiation and/or to
sound energy.
DETAILED DESCRIPTION
Brief Description of the Drawings
[0019] FIG. 1 Illustrates the fundamental principal the reaction of
a pressure sensitive adhesive with a modified filler.
[0020] FIG. 2 illustrates the deprotection or deblocking of the
group Z to form the group X.
[0021] FIG. 3 illustrates the reaction of group X with functional
group Y.
[0022] FIG. 4 illustrates two examples of the coupling of reactive
constituents via formation of hydrogen bonds.
[0023] FIG. 5 diagrammatically illustrates the coupling
principle.
[0024] FIG. 6 illustrates the formation of coordinate bonds with
acceptor group (key) M in conjunction with a donor group of the
"lock" type.
[0025] FIG. 7 illustrates Inventive constructions of self-adhesive
products, and
[0026] FIG. 8 illustrates the addition of filler particles,
particle dispersions and coupling reagents to the hotmelt adhesives
at different metering points
[0027] The present invention relates to a process for preparing a
crosslinked pressure-sensitive adhesive, to crosslinked
pressure-sensitive adhesives obtainable by such a process, and to
the use of such adhesives. The invention further embraces
intermediates from such a process, particularly the composition of
innovative formulations for pressure-sensitive adhesives. The
combination of the innovative PSA formulations of the invention
with the preparation process of the invention is likewise inventive
and a central component of this specification (in this regard cf.
also FIG. 1). FIG. 1 shows the fundamental principle of how a
pressure-sensitive adhesive formulation is reacted by means of a
modified filler, via an operation which includes, in particular,
compounding, the coating of the composition onto a carrier, and the
subsequent crosslinking of the composition, to give a crosslinked
pressure-sensitive adhesive.
[0028] The invention provides a process for preparing a
pressure-sensitive adhesive comprising the crosslinking product of
at least one polymer and at least one kind of functionalized
particles, [0029] the polymer having reactive centres, [0030] the
functionalized particles having at least one nonpolymeric base
unit; the nonpolymeric base unit has a surface modification, the
surface modification of the nonpolymeric base unit having at least
one kind of functional groups Z which under the conditions during
the preparation and processing of the polymer and/or of the
noncrosslinked pressure-sensitive adhesive do not enter into any
reaction with the reactive centres of the polymer, characterized in
that the process comprises the following steps: [0031] converting
at least some of the functional groups Z of the particles, by
supply of energy, overcoming the activation energy of conversion,
into functional groups X which are capable, under appropriate
process conditions, of entering into a reaction with the reactive
centres of the polymer, [0032] forming the crosslinking product,
comprising reacting the functional groups X of the particles with
the reactive centres of the polymer under the appropriate process
conditions.
[0033] In a particularly preferred procedure, the supplied energy
is thermal energy, electromagnetic radiation, particulate radiation
and/or sound energy.
[0034] In one very advantageous embodiment of the process the
reactive centres are functional groups Y.
[0035] The invention accordingly relates to a process for preparing
a pressure-sensitive adhesive based on at least one polymer A, in
the course of which said at least one polymer A is crosslinked, it
being possible for the polymer to have functional groups Y and
having been admixed, further, with at least one kind of
functionalized particles B (also called "filler particles" below).
The particles have at least one nonpolymeric base unit and also a
surface modification of this base unit, the surface modification of
the base unit having at least one kind of functional groups Z,
which are protected or blocked groups X and which are only
converted into the group X by means of external stimuli (e.g.,
temperature, actinic radiation, ultrasound) by decomposition,
dissociation (homolytically or heterolytically) or by other
chemical reactions (see FIG. 2: deprotection or deblocking of the
group Z to form the group X). In accordance with the invention the
crosslinking of the polymer is brought about at least in part by a
reaction of the functional groups X of the particles and the
polymer, it being possible for the latter to comprise functional
groups Y. The group Z per se is not conducive to crosslinking with
the polymer A and must therefore be transformed first of all into
group X. Within the sense of the invention the crosslinking may
also be brought about completely by means of the functionalized
particles.
[0036] The dependent claims relate to advantageous versions of the
process of the invention.
[0037] The invention further provides a pressure-sensitive adhesive
based on at least one crosslinked polymer component A, the
crosslinking of the polymer component A being brought about at
least in part by incorporation of functionalized particles B, the
particles B having at least one nonpolymeric base unit and also a
surface modification of this base unit, and the surface
modification of the particles B having at least one kind of blocked
or protected functional groups X which, after activation, are
capable of reacting with polymer component A, it being possible for
functional groups Y to be present in the polymer component A.
[0038] A pressure-sensitive adhesive of this kind is to be
presented as being in accordance with the invention particularly if
it is obtainable by the processes described as being in accordance
with the invention.
[0039] The invention additionally provides for the use of
surface-modified particles having a nonpolymeric base unit,
particularly of particles of the kind described in the context of
this specification, as crosslinking reagents of polymers for
preparing pressure-sensitive adhesives.
[0040] Also considered as being in accordance with the invention
are the polymers A which have as yet not been crosslinked but have
been admixed with the functionalized particles B. In the
pressure-sensitive adhesive to be crosslinked there may be further
components present.
[0041] The PSA formulations of the invention comprise at least one
kind of a polymer A which may contain at least one kind of groups
of type Y, and also at least one kind of filler particles B
containing on their surface at least one kind of groups of type X
which originates, as a result of activation, from a group of type Z
which is not suitable for crosslinking. The group of type Z has
been selected for the purposes of the invention such that the group
of type X is generated therefrom by exposure to thermal energy,
electromagnetic radiation, particulate radiation and/or sound
energy, which group of type X is formed in turn independently or in
combination with the protection or conversion of group Z and also
that exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy forms a bond between the
polymer and at least one functional group of type X and/or at least
one group in the polymer of type Y and at least one functional
group of type X, thereby producing an adduct of type B--X'-A
(reaction with reactive centre) and/or B--X'--Y'-A (reaction with
functional group Y) (see FIG. 3). The designation X' here denotes
that the structure of the functional group X may have altered
following reaction. Similarly, the designation Y' indicates that
the structure of the functional group Y may have altered following
reaction. It is likewise in accordance with the invention for the
functional groups X and Y not to have altered in their structure
and yet still to have entered into a linkage.
[0042] In this description the terms "electromagnetic radiation"
and "particulate radiation" are to be understood to mean all forms
of radiation, a summary having been given by V. D. McGinniss [V. D.
McGinniss in Encyclopedia of Polymer Science and Engineering, H. F.
Mark, N. M. Bikales, C. G. Overberger, G. Menges (eds.), 2nd ed.,
1986, Wiley, New York, vol. 4, p. 418ff]. The skilled worker is
aware of further kinds of radiation, which can likewise be employed
inventively. The use of sound energy, more particularly ultrasound,
is likewise becoming ever more significant in chemical reactions
and is employed in practice [E. B. Flint, K. S. Suslick; Science
1991, 253, 1397ff]. The use of thermal energy can be employed with
preference in accordance with the invention.
[0043] Through the inventive use of the innovative formulations
described here, in combination with the process described here,
advantageously crosslinked PSAs are obtained. The functionalized
filler particles B act as polyfunctional crosslinkers [DE 10 2005
022 782]. As a result of their capacity to link two or more polymer
chains in one crosslinking point it is possible to reduce the molar
mass of the polymeric constituents of the PSA that are to be
crosslinked (on the basis of polymeric constituents for the PSA
which--in relation to customary, prior-art processes--have a
reduced molar mass). There follows an improvement in the processing
characteristics. Conversely, within the context of this invention,
it is also possible to admix the filler particles of the invention
to PSAs which comprise crosslinkable polymers of low molar mass.
Following exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy, different network
structures are obtained than if the filler particles of the
invention had not been present. A feature of this innovative state
of crosslinking is that it correlates with improved product
properties, particularly an increased cohesion of the PSA.
Typically it is characteristic of the innovative state of
crosslinking that the adhesive properties of the PSAs of the
invention are at least at the level also occupied by a crosslinked
PSA which contains no inventive filler particles but has been
processed in a comparable way and has a comparable gel
fraction.
[0044] An advantageous approach is for the PSA formulations of the
invention, comprising at least one kind of an inventive polymer A
and at least one kind of a functionalized filler particle B, to
have good processing properties in the raw state--that is, before
processing commences. By processing properties for the purposes of
this invention are meant in particular the viscosity of the PSA
formulation and also its elasticity. The viscosity is reported as
zero-shear viscosity .eta..sub.0 for different temperatures. It can
be obtained from viscosity curves determined by capillary
viscosymmetry. The elasticity is reported in the form of the first
normal stress difference N.sub.1, again at different temperatures.
The data for the first normal stress difference, too, can be
obtained from capillary viscosymmetry experiments. Both variables,
the viscosity and the first normal stress difference, are generally
dependent on shear rates for PSA formulations. Depending on process
and the shear rates which occur therein, therefore, they may vary
for a given PSA formulation. For the description of this invention
it is sensible to limit oneself to one shear rate; however, this
does not restrict in this respect the processes which can be used
in accordance with the invention. As one such shear rate the shear
rate of 1000 s.sup.-1 is selected as a representative, advantageous
value. For the processing properties and particularly the
coatability it is very advantageous not to exceed a defined ratio
of elasticity and viscosity at the shear rate dictated by the
process. If this ratio is too high, the elastic character of the
material to be coated is predominant. A consequence of that can be
melt fracture, which is manifested in a non-homogeneous coating
pattern (M. Pahl, W. Glei.beta.le, H.-M. Laun, Praktische Rheologie
der Kunststoffe und Elastomere, 4th ed., 1995, VDI Verlag,
Dusseldorf, p. 191f).
[0045] In accordance with information gained from
capillary-viscosimetric rheology, the ratio R.dbd.N.sub.1/.tau. of
first normal stress difference N.sub.1 and shear stress .tau.
determines the processing characteristics of a polymer melt [W.
Glei.beta.le, Rheol. Acta, 1982, 21, 484-487; M. Pahl, W.
Glei.beta.le, H.-M. Laun, Praktische Rheologie der Kunststoffe und
Elastomere, 4th ed., 1995, VDI Verlag, Dusseldorf, p. 320ff]. The
shear stress .tau. is the product of viscosity and shear rate. The
numerator of the ratio N.sub.1/.tau. hence describes the elastic
properties of the material, the denominator the viscous properties.
The latter, moreover, illustrates the dependence on the operating
speed in the form of the shear rate. Above a critical rate for R,
flow anomalies occur. If, therefore, at the shear rates which
prevail during processing, success is achieved in reducing N.sub.1
by a design of material, or at least in not causing it to grow
further as a result of additional crosslinking effects, the
expectation is then that the material will be able to be coated
without melt inhomogeneities. This can be accomplished, for
example, by not initiating crosslinking until after coating, such
as is possible, for example, in the case of radiation treatment.
The irradiated and thus crosslinked material has an increased
elasticity and, in association with this, a higher first normal
stress difference, and in this state could not be processed with a
good coating pattern. The uncrosslinked melt, however, is less
elastic, exhibits a lower first normal stress difference, and can
be coated successfully. For PSAs with good cohesion there is
frequently a need for polymers having high molar masses.
[0046] These polymers, however, may have high elasticities even in
the chemically uncrosslinked state, owing to intermolecular
interactions, such as interlooping, and this may lead to
disadvantages in the coating characteristics.
[0047] The innovative invention follows the concept of
accomplishing the cohesion of the PSA of the invention essentially
by means of an improved state of crosslinking via chemical linking
of polymers to filler surfaces. A high polymer molar mass is
therefore no longer mandatory and, consequently, the coating
characteristics are not so pronouncedly restricted as a result of
chain interlooping. The particles themselves, during processing,
are in the form of a disperse phase in the PSA formulation. Since
at this time they have not yet undergone chemical linkage with
polymeric constituents of the formulation, at this time their
contribution to the elasticity of the formulation is incomplete.
Only when the crosslinking reaction is initiated, during and/or
after coating, is the desired cohesion produced. The requirements
imposed on the PSA formulations of the invention are therefore that
the formulation in the uncrosslinked state should exhibit good
processing properties, provided for example by a low first normal
stress difference, and in particular the ratio R, and in the
crosslinked state should exhibit good cohesion, provided for
example by the holding power or the gel fraction of a self-adhesive
tape test specimen. The innovative concept of the invention
likewise includes the use and coating of pressure-sensitive
adhesive formulations in solution, but where the problems described
above are fairly insubstantial. The prior art, however, still has
potential for improvement in respect of the crosslinking reaction
between particles and polymer. The present invention proposes
innovative solutions for this.
[0048] Advantageous PSAs of the invention, obtained by way of the
inventive coating and crosslinking operation, typically have a
holding power according to test D that is at least 50% higher,
preferably at least 100% higher, than that of a formulation coated
and crosslinked in exactly the same way but containing no filler
particles of the invention and yet having a comparable gel fraction
(test B). The adhesion, given by the bond strength according to
test C, of the PSA system of the invention is typically at least at
the same level occupied by that of the aforementioned reference
system, or preferably is in fact at least 25% higher. At the same
time, the R value of the inventive PSA in the uncrosslinked state,
at a temperature which is appropriate in a way that is specific to
the particular material, of between 25.degree. C. and 300.degree.
C., exhibits virtually no increase, likewise in comparison to a
formulation that contains no filler particles of the invention and
is also uncrosslinked, and remains at values of preferably not more
than R=3.5 (test A2). The viscosity of the PSAs of the invention at
the same temperature is no higher or only slightly higher,
specifically not more than, preferably, 25% higher, than that of a
formulation that contains no filler particles of the invention and
is also uncrosslinked (test A1).
Composition of Inventive PSA Formulations
[0049] The PSA formulations of the invention comprise at least one
kind of polymer, A, and at least one kind of filler particle, B,
the at least one polymer kind A being able to join with groups X,
located on the surface of the at least one filler particle kind B,
through exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy during and/or after a
coating operation. The polymer may carry groups of type Y, which
are capable of reaction with the functional group X. The group X,
bound on the surface of the at least one filler kind B, originates
from a group Z, which is likewise bound on the surface of the same
particles, by means of thermal activation or through
electromagnetic radiation, particulate radiation and/or sound
energy--referred to merely as activation below; the group of type Z
per se is not suitable for crosslinking reactions. The PSA of the
invention may optionally comprise further constituents in addition
to polymers A and filler particles B. This section will address the
polymers A of the invention, the fillers B of the invention, and
further constituents which may be used optionally in the PSA
formulations of the invention, and will also describe the nature of
the groups X, Y and Z.
[0050] The PSAs of the invention contain advantageously up to 50%
by weight of at least one filler particle kind B, preferably up to
20% by weight, very preferably up to 10% by weight.
Polymers A
[0051] The at least one polymer kind A is preferably in accordance
with the invention when it has a molar mass of not more than 10 000
000 g/mol, preferably not more than 500 000 g/mol. Furthermore, the
at least one polymer kind A preferably has a softening temperature
of less than 100.degree. C., more preferably less than 20.degree.
C. The at least one polymer kind A may be of linear, branched,
star-shaped or grafted structure, to give but a few examples, and
may be in the form of a homopolymer or copolymer. The term
"copolymer" encompasses for the purposes of this invention not only
copolymers in which the comonomers used for the polymerization have
been incorporated in purely random fashion but also those in which
there are gradients in the comonomer composition and/or local
accumulations of individual comonomer kinds and also entire blocks
of a monomer in the polymer chains.
[0052] The molar mass is to be understood in this context as
referring to the weight average of the molar mass distribution, as
is obtainable, for example, via gel permeation chromatography
analyses. By softening temperature in this context is meant the
glass transition temperature for amorphous systems and the melting
temperature for semicrystalline systems, and may be determined, for
example, by dynamic differential calorimetry (DSC). Where numerical
values are given for softening temperatures, they relate in the
case of amorphous systems to the middle-point temperature of the
glass stage and in the case of semicrystalline systems to the
temperature at maximum heat evolution during the phase
transition.
[0053] Within the sense of this invention it is possible, moreover,
for the at least one polymer kind A to be a block copolymer. Of
particular advantage are block copolymers in which, preferably,
each of the blocks present (independently of one another) has a
molar mass of less than 1 000 000 g/mol, preferably less than 250
000 g/mol, is of linear, branched, star-shaped or grafted structure
and/or is in the form of a homopolymer or random copolymer. With
further advantage at least one kind of block has a softening
temperature of less than 100.degree. C., preferably less than
20.degree. C. The individual kinds of block occurring in the block
copolymer may differ with regard to the comonomer composition and
optionally may differ in their molar mass and/or softening
temperature and/or structure (e.g., linear or branched identity).
The different polymer arms in star-shaped and grafted systems may
be chemically different in nature: that is, may be composed of
different monomers and/or may have a different comonomer
composition.
[0054] Polymers of kind A are also preferred in accordance with the
invention when they are able to enter into a bond, during or after
a coating operation, without reactive groups or with at least one
kind of groups Y present in the polymer with groups of type X
present on the surface of the at least one filler particle kind B,
on exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy. The groups X originate,
by means of activation through thermal energy, electromagnetic
radiation, particulate radiation and/or sound energy, from the
groups Z, which in turn, without activation and conversion into the
functional groups X, are unable to enter into any crosslinking
reactions, and hence make it possible to control the operation. The
groups of the at least one kind Y may be present in a diversity of
ways in the at least one polymer kind A. The at least one polymer
kind A may be constructed, for example, as a homopolymer from
monomers which contain the at least one kind of groups Y.
Furthermore, the at least one polymer kind A may also be
constructed as a random copolymer which is obtained at least from
one kind of monomers which contain the at least one kind of groups
Y and, optionally, from one or more kinds of monomers which contain
no such groups. A further possibility is for the at least one
polymer kind A to contain the at least one kind of groups Y only at
certain points along the polymer backbone. Examples of such
embodiments include groups which are located at chain ends, in the
region of chain points or blocking-agent points, in the region of
branching points or in the region of block connection points.
Polymers of the at least one kind A are particularly preferred in
accordance with the invention when the polymer molecule contains on
average at least two such groups. It is possible, furthermore, for
the at least two groups Y to be introduced into the at least one
polymer A by way of a grafting reaction. It is likewise in
accordance with the invention to introduce the at least two groups
Y into the at least one polymer kind A by carrying out a
polymer-analogous reaction. Furthermore, any desired combinations
of the stated modes of functionalization are in accordance with the
invention.
[0055] As examples of polymers A, but without wishing to impose any
restriction, mention may be made of the following homopolymers and
random copolymers as being advantageous for the purposes of this
invention: polyethers, such as polyethylene glycol, polypropylene
glycol or polytetrahydrofuran, polydienes, such as polybutadiene or
polyisoprene, hydrogenated polydienes, such as
polyethylene-butylene or polyethylene-propylene, rubbers, such as
natural rubber, nitrile rubber or chloroprene rubber, butadiene
rubber, isoprene rubber, and polyisobutylene, polyolefins, such as
ethylene homopolymers or copolymers, propylene homopolymers or
copolymers, metallocene-catalyzed polyolefins, polysiloxanes,
polyalkyl vinyl ethers, polymers of unfunctionalized
.alpha.,.beta.-unsaturated esters, copolymers based on
.alpha.,.beta.-unsaturated esters, copolymers based on alkyl vinyl
ethers, and also ethylene-vinylacetate copolymers, EPDM rubbers,
and styrene-butadiene rubbers. Further random copolymers which can
be used with advantage are obtained by copolymerizing isoprene
and/or butadiene, feature 1,4, 1,2 and/or 3,4, or 1,4 and/or 1,2,
incorporation of the monomers into the polymer chain, and may be in
fully or partly hydrogenated form.
[0056] Copolymers which can be used with particular advantage for
the purposes of this invention are random copolymers based on
unfunctionalized .alpha.,.beta.-unsaturated ethers. When they are
used for the at least one polymer kind A with copolymer character,
then monomers which can be used for their preparation are,
advantageously, in principle all compounds familiar to the skilled
worker that are suitable for polymer synthesis. Preference is given
to using .alpha.,.beta.-unsaturated alkyl esters of the general
structure
CH.sub.2.dbd.CH(R.sup.1)(COOR.sup.2) (1)
where R.sup.1.dbd.H or CH.sub.3 and R.sup.2.dbd.H or represents
linear, branched or cyclic, saturated or unsaturated alkyl radicals
having 1 to 30, in particular having 4 to 18, carbon atoms.
[0057] Monomers which can be used with great preference in the
sense of general structure I for polymers A with copolymer
character include acrylic and methacrylic esters with alkyl groups
consisting of 4 to 18 carbon atoms. Specific examples of such
compounds, without wishing to be restricted by this enumeration,
include n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate,
n-pentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate,
n-heptyl acrylate, n-heptyl methacrylate, n-octyl acrylate, n-octyl
methacrylate, n-nonyl acrylate, n-nonyl methacrylate, n-decyl
acrylate, n-decyl methacrylate, dodecyl acrylate, dodecyl
methacrylate, hexadecyl acrylate, hexadecyl methacrylate, octadecyl
acrylate, octadecyl methacrylate, their branched isomers, such as
sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate,
tert-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl
methacrylate, and isooctyl acrylate, and also cyclic monomers such
as, for example, cyclohexyl acrylate, cyclohexyl methacrylate,
norbornyl acrylate, norbornyl methacrylate, isobornyl acrylate and
isobornyl methacrylate.
[0058] Likewise possible for use as monomers for polymers A with
copolymer character are acrylic and methacrylic esters which
contain aromatic radicals, such as phenyl acrylate, benzyl
acrylate, benzoin acrylate, benzophenone acrylate, phenyl
methacrylate, benzyl methacrylate, benzoin methacrylate or
benzophenone methacrylate.
[0059] A further possibility for use in accordance with the
invention are ethoxylated and propoxylated acrylates and
methacrylates. In systems of this kind the acrylate or methacrylate
side chains are composed formally of an oligomer or polymer or
ethylene oxide or of propylene oxide.
[0060] It is additionally possible, optionally, to use vinyl
monomers from the following groups: vinyl esters, vinyl ethers,
vinyl halides, vinylidene halides, and also vinyl compounds
containing aromatic rings and heterocycles in a position. For the
vinyl monomers which can be employed optionally, mention may be
made by way of example of selected monomers which can be used in
accordance with the invention: vinyl acetate, vinylformamide,
vinylpyridine, ethyl vinyl ether, 2-ethylhexyl vinyl ether, butyl
vinyl ether, vinyl chloride, vinylidene chloride, acrylonitrile,
styrene, and .alpha.-methylstyrene.
[0061] In one preferred version of this invention the at least one
polymer kind A contains its at least two groups Y in the form of at
least one specific comonomer which has been randomly copolymerized
during the polymerization of the polymer. The molar fraction
(chemical amount fraction) of this at least one specific comonomer
in relation to the composition of the total monomer mixture during
the preparation of the total polymer is up to 50% by weight,
preferably up to 20% by weight, very preferably up to 5% by weight.
The specific character of this at least one comonomer is expressed
in the fact that it carries at least one group Y which is able to
enter into a bond, during or after a coating operation, with at
least one group X originating from a protective group Z, located on
the surface of the at least one filler particle kind B, on exposure
to thermal energy, electromagnetic radiation, particulate radiation
and/or sound energy. Examples of groups X, Y and Z are described in
the section "Combinations of groups X, Y and Z". Particular
preference is given to using monomers based on
.alpha.,.beta.-unsaturated esters which contain these groups. It is
also possible for groups Y to be joined by way of a
polymer-analogous reaction with the polymer A at the sites at which
these specific comonomers have been incorporated. A further
possibility is for these specific comonomers to be derivatized with
groups Y prior to polymerization; in other words, for comonomers
with functionalization which is not necessarily in accordance with
the invention to be modified, prior to polymerization and hence
preparation of a polymer kind of type A, with a chemical assembly
via which the at least one inventive group Y is incorporated into
the comonomer and, following this modification reaction and
subsequent polymerization, is available for the forming of a
linkage, in accordance with the invention, with at least one group
X.
[0062] As examples of comonomers which carry functional groups,
mention may be made--without wishing to impose any restriction--of
allyl acrylate, allyl methacrylate, tetrahydrofurfuryl acrylate,
tetrahydrofurfuryl methacrylate, 2-hydroxyethyl acrylate,
2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate,
3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate,
4-hydroxybutyl methacrylate, glycidyl acrylate, glycidyl
methacrylate, acrylated benzophenone, methacrylated benzophenone,
crotonic acid, maleic acid, maleic anhydride, itaconic acid,
itaconic anhydride, 2-dimethylaminoethyl acrylate,
2-dimethylaminoethyl methacrylate, 3-dimethylaminopropyl acrylate,
3-dimethylaminopropyl methacrylate, N-tert-butylacrylamide,
N-tert-butylmethacrylamide, N-isopropylacrylamide,
N-isopropylmethacrylamide, acrylamide, methacrylamide,
N-methylolacrylamide, N-methylolmethacrylamide, acrylic acid,
methacrylic acid, vinyl alcohol, 2-hydroxyethyl vinyl ether,
3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether and allyl
glycidyl ether.
[0063] If the at least one polymer kind A is a block copolymer then
in the simplest case the copolymers present are diblock copolymers
of the form PA-PA', composed of a block PA and a block PA', which
differ in respect of the starting monomers selected and may
optionally be different in their softening temperature and/or molar
mass and/or structure (e.g., linear or branched). Further
embodiments of polymers A with block copolymer character, without
wishing to impose any restriction, are triblock copolymers of the
type PA-PA'-PA'', block copolymers of the type PA-PA'-PA''-PA', and
higher block copolymers whose structures continue this series.
Triblock copolymers and higher block copolymers are in accordance
with the invention, in the sense of polymers A with block copolymer
character, when all blocks linked directly to one another are
different in respect of the selected starting monomers and also,
optionally, in their molar mass and/or softening temperature and/or
structure (e.g., linear or branched). Further, triblock copolymers
and higher block copolymers are in accordance with the invention,
in the sense of polymers A, if two or more of the blocks which are
not linked directly to one another are not different from one
another in respect of the selected starting monomers and also,
optionally, in their molar mass and/or softening temperature and/or
structure (e.g., linear or branched). A preferred version of a
polymer A with block copolymer character is a triblock copolymer of
the type PA-PA'-PA'', where PA and PA'' are identical in respect of
the selected starting monomers, molar mass, softening temperature,
and structure. The block linkage in polymers A with block copolymer
character may take a linear form or alternatively a star-shaped
embodiment, or a graft copolymer variant. Each individual block may
be constructed as a homopolymer block or copolymer block. The
blocks are therefore subject to the same definitions as given in
the section "Homopolymers" and "Random copolymers".
[0064] Where a block copolymer is employed as polymer A, then
preferably at least one kind of block contains functionalizations
of type Y. Particular preference is given to diblock copolymers
which contain functionalizations of type Y in only one kind of
block; symmetrical triblock copolymers which contain
functionalizations of type Y only in two end blocks; and triblock
copolymers which contain functionalities of type Y only in the
middle block.
Filler Particles B
[0065] As the at least one filler particle kind B for the purposes
of this invention use is made preferably of filler particles in
which the base units without surface modifications have softening
temperatures of greater than 80.degree. C., preferably of greater
than 120.degree. C. Furthermore, systems of the kind whose
softening temperature (based on the unmodified base units) is above
the decomposition temperature are in accordance with the invention
when the decomposition temperature is above 200.degree. C.,
preferably above 500.degree. C.
[0066] The materials on which the base unit of the at least one
filler particle kind B is based may be inorganic in nature or may
be an organic/inorganic hybrid material and may have an amorphous,
partly crystalline or crystalline character.
[0067] In terms of their structure, the filler particles may be
present preferably in spherical form, rodlet form or platelet form.
Separate particles, often also called primary particles, are in
accordance with the invention just as much as aggregates formed
from a plurality of primary particles. Such systems often exhibit a
fractal superstructure. Where the particles are formed from
crystallites, the primary particle form depends on the nature of
the crystal lattice. Platelet-form systems can also be present in
the form of layer stacks.
[0068] In one advantageous embodiment of this invention the at
least one functionalized filler kind is present in the
pressure-sensitive adhesive substantially in the form of singular
spherical particles. In that case the particle diameters have
values of less than 2 .mu.m, preferably of less than 250 nm, very
preferably of less than 25 nm. In a further advantageous version of
this invention the at least one functionalized filler kind is
present in the pressure-sensitive adhesive substantially in the
form of singular platelet-shaped particles. The layer thickness of
such platelets then has values of preferably less than 10 nm and a
greatest diameter of preferably less than 1000 nm. In a further
advantageous version of this invention the at least one filler kind
is present in the pressure-sensitive adhesive substantially in the
form of singular rodlet-shaped particles. In this case these
rodlets have a diameter of less than 100 nm and a length of less
than 15 .mu.m. The rodlets may also be curved and/or flexible.
Furthermore, it is possible with advantage for the purposes of this
invention for the at least one filler kind to be present in the
pressure-sensitive adhesive in the form of primary particle
aggregates. These aggregates have a gyration radius (to be
understood in analogy to the term "radius of gyration" as known
from polymers) of less than 1000 nm, preferably of less than 250
nm. Particular preference is given for the purposes of this
invention to using filler particles of the kind whose spatial
extent in at least one direction is less than 250 nm, preferably
less than 100 nm, very preferably less than 50 nm. It is possible
for the purposes of this invention, furthermore, to use
combinations of the aforementioned types of filler.
[0069] In one particularly advantageous embodiment of this
invention the particles or particle aggregates described above are
present in the form of stable dispersions, which significantly
simplifies processing. The dispersion medium in this case
may--without wishing to impose any restriction--be water, organic
solvents such as ethanol, isopropanol, acetone, methyl ethyl
ketone, methyl isobutyl ketone, toluene, xylene, for example,
reactive systems such as the above-described monomers for preparing
the PSAs, or a polymeric binder.
[0070] The functionalized particles may possess various
morphologies; with particular advantage it is possible to use
spherical, rodlet-shaped and/or platelet-shaped particles and/or
aggregates of the aforementioned forms of appearance. Particularly
advantageous results have been achieved with aggregates.
[0071] Typical classes of compound, advantageous in accordance with
the invention, of which the base unit of the at least one filler
particle kind B is composed are oxides of inorganic
nature--particularly metal oxides and/or semimetal oxides--salts of
alkaline earth metals, and silicate-based minerals, especially clay
minerals and clays. The amorphous or crystalline metal oxides that
can be used in accordance with the invention include, for example,
silicon dioxide (as a solid: e.g. Degussa AG, Aerosil.RTM.; Cabot,
CAB-O-SIL.RTM.; in a dispersion e.g. Clariant International AG,
Highlink.RTM.; Degussa AG, Aerosil.RTM.; Nissan Chemical America
Corporation, Organosilicasol.TM.; Byk Chemie GmbH, Nanobyk.RTM.;
Hanse Chemie, Nanocryl.RTM.; Cabot, CAB-O-SPERSE.RTM.), aluminum
oxide (e.g. Degussa-AG, Aeroxide.RTM.), titanium dioxide, zirconium
dioxide (e.g. Byk Chemie GmbH, Nanobyk.RTM.), and zinc oxide (e.g.
Umicore, Zano.RTM.). The skilled worker is familiar with further
systems, which may likewise be used in accordance with the
invention. Alkaline earth metal salts include, for example,
carbonates, sulphates, hydroxides, phosphates, and hydrogen
phosphates of magnesium, of calcium, of strontium, and of barium.
The clay minerals and clays which can be used in accordance with
the invention include, in particular, silicatic systems such as
serpentines, kaolins (e.g. Hoffmann Mineral GmbH, Silitin.RTM.,
Aktisil.RTM. (mixture of quartz and kaolinites)), talc,
pyrophyllite, smectites such as particularly montmorillonite (e.g.
Sud-Chemie, Nanofil.RTM. and Cloiste.RTM. from Southern Clay
Products, Inc.), vermiculites, illites, mica, brittle mica,
chlorites, sepiolite, and palygorskite. Additionally it is possible
to use synthetic clay minerals such as hectorites and also systems
related thereto, such as Laponite.RTM. from Rockwood Holdings Inc.
and fluorohectorites and systems related thereto, such as
Somasif.RTM. from Co-Op, in accordance with the invention.
[0072] The at least one filler particle kind B is in a
surface-modified form. Surface modification reagents that are
typical and advantageous in accordance with the invention are
organosilanes (e.g. Wacker-Chemie GmbH, Geniosil.RTM., Degussa AG,
Dynasylan.RTM., GE Silicones, Silquest.RTM.; Gelest, Inc.) and
surfactants, but also organotitanium compounds (e.g. Dupont,
Tyzor.RTM.; Kenrich Petrochemicals, Inc., Lica.RTM.), fatty acids
or polyelectrolytes such as, for example, short-chain polymers
having a high acrylic acid fraction. The primary function of these
surface modification reagents is to create compatibility between
the particle surface and the matrix into which the particles are to
be dispersed. As a further function, surface modification reagents
are used in order to prevent relatively small particles coming
together to form larger objects. It is very advantageous for the
purposes of the invention to use at least one kind of surface
modification reagent which in addition to the compatibilizing and
aggregation-preventing function also affords the possibility of
entering, via at least one group X incorporated in the at least one
kind of surface modification reagent, into a connection with the
polymer A and/or at least one group Y, present in at least one
polymer kind A, on exposure to thermal energy, electromagnetic
radiation, particulate radiation and/or sound energy, during or
after a coating operation. The group X is initially in blocked or
deactivated form, as a group of type Z, which per se is not capable
of a crosslinking reaction with the at least one polymer kind A
and/or with a group Y present in the polymer A, and is converted
into the group X only by external activation, by decomposition or
other chemical reactions. The external influences for activating
this conversion may likewise be thermal energy, electromagnetic
radiation, particulate radiation and/or sound energy. Advantageous
in this case is thermal activation, in which case, in one
particularly advantageous form of the group Z, the activation
temperature is above or the same as the operating temperature, so
that the crosslinking is initiated only after the coating. A filler
particle carries on its surface preferably at least 10 groups of
the at least one kind Z, more preferably at least 50.
[0073] In one advantageous embodiment of the process of the
invention the functionalized particles, on the same base units on
which the functional groups Z are provided, and/or on further
nonpolymeric base units, additionally have functional groups
X.sub.a, the groups X.sub.a being capable, under appropriate
process conditions, of entering into a reaction with the reactive
centres, more particularly the functional groups Y of the polymer,
and, in the process, even before the conversion of the groups Z
into the groups X, a crosslinking step takes place which comprises
reacting the functional groups X.sub.a with the reactive centres,
more particularly the functional groups Y of the polymer.
[0074] A further inventively advantageous embodiment of the
surface-modified filler kind B comes about through a combination of
the surface modification reagents, with one kind containing at
least one functional group Z which, following activation by thermal
energy, electromagnetic radiation, particulate radiation and/or
sound energy, undergoes decomposition or is chemically converted to
form the group X, and another kind comprising at least one kind
X.sub.a which not only differs chemically from the functional group
of the type X but also contributes by a different reaction
mechanism to the crosslinking with the polymer of kind A. This
crosslinking reaction may be initiated by thermal energy,
electromagnetic radiation, particulate radiation and/or sound
energy; the functional groups X and X.sub.a are not activated by
the same external stimuli, so providing the possibility for the
formulation of a pressure-sensitive adhesive featuring a dual-cure
system. Thus, for example, it is possible, with two kinds of groups
X and X.sub.a, having different reactivities and/or different
activation mechanisms, first to carry out partial crosslinking of
oligomers or polymers, so that a specific viscosity range is
acquired, which simplifies the processing, and then, after the
coating, initiating an aftercure reaction.
[0075] Filler particles which in their natural form (in the form of
the base unit without surface modification) contain hydroxide
groups on the surface afford the possibility, preferably, of a
reaction with chlorosilanes or alkoxysilanes. Hydrolysis of the
silane is followed by condensation of silanol groups with the
hydroxide groups on the particle surface. If at least one
substituent on the central silicon atom of the silane is an organic
radical, then in the case of complete surface coverage with silane
molecules an organophilic casing is linked covalently in this way
to the filler particle, and hence the particles are made compatible
with the polymer matrix. The concepts and typically used classes of
material which can be employed for the purposes of this invention
are described, for example by R. N. Rothon [R. N. Rothon (ed.),
"Particulate-Filled Polymer Composites" 2nd ed., 2003, Rapra
Technology, Shawbury, 153-206].
[0076] Two classes of silanes can be distinguished in particular
for the purposes of this invention: on the one hand, those which,
in addition to the groups capable of reaction with the base
surface, carry exclusively organic radicals which are chemically
inert (see structure II); on the other, those which, in addition to
the groups capable of reaction with the base surface, contain at
least one organic radical which carries at least one group X or Z
that is able to enter into a bond, directly and/or after
activation, with the polymer kind A and/or at least one group Y
present in at least one polymer kind A on exposure to thermal
energy, electromagnetic radiation, particulate radiation and/or
sound energy, during or after a coating operation (see structure
III). In silane II at least one of substituents A, B, and D is a
hydrolyzable group, i.e., a chlorine atom or an alkoxy group, for
example. At least one of substituents B, C, and D is an organic
radical which is composed of a linear, branched or cyclic
hydrocarbon, which may also be aromatic and is of low molecular
mass or oligomeric or polymeric in nature. If there is more than
one hydrolyzable group among substituents A, B, and D, then the
groups involved may be chemically identical or different, or
meeting the above definition of hydrolyzable groups. If there is
more than one organic radical among substituents B, C, and D, then
these radicals may likewise be chemically identical or different,
or meeting the above definition of organic radicals. In silane III
at least one of substituents A, E, and F is a hydrolyzable group,
i.e., a chlorine atom or an alkoxy group, for example. At least one
of substituents E, F, and G is an organic radical which is composed
of a linear, branched or cyclic hydrocarbon, which may also be
aromatic and is of low molecular mass or oligomeric or polymeric in
nature and which additionally contains at least one group X or Z
which is able, during or after a coating operation, to enter,
directly or after activation, into a bond with the polymer kind A
and/or at least one group Y present in at least one polymer kind A
on exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy. If there is more than
one hydrolyzable group among substituents A, E, and F, then the
groups involved may be chemically identical or different. If there
is more than one organic radical among substituents E, F, and G,
then the radicals involved may likewise be chemically identical or
different, or meeting the above definition of organic radicals.
##STR00001##
[0077] Advantageous embodiments of silanes of structure II that are
useful in accordance with the invention are those in which only A
is employed as a hydrolyzable group and B, C, and D are organic
radicals, of which B and D are chemically identical and C has
chemically different properties. Further advantageous embodiments
of silanes of structure II that are useful in accordance with the
invention are those in which A and B are employed as chemically
identical hydrolyzable groups and C and D are chemically identical
organic radicals. Further advantageous embodiments of silanes of
structure II that are useful in accordance with the invention are
those in which A, B, and D are employed as chemically identical
hydrolyzable groups and C is an organic radical.
[0078] Advantageous embodiments of silanes of structure III that
are useful in accordance with the invention are those in which only
A is employed as a hydrolyzable group and E, F, and G are organic
radicals, of which E and F are chemically identical and G is
chemically different. G contains the at least one group X or Z
which, during or after a coating operation, is able to enter,
directly or after activation, into a bond with the polymer kind A
and/or at least one group Y present in at least one polymer kind A
on exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy. Further advantageous
embodiments of silanes of structure III that are useful in
accordance with the invention are those in which A, E, and F are
employed as chemically identical hydrolyzable groups and G is an
organic radical which contains the at least one group X or Z which,
during or after a coating operation, is able to enter, directly or
after activation, into a bond with the polymer kind A and/or at
least one group Y present in at least one polymer kind A on
exposure to thermal energy, electromagnetic radiation, particulate
radiation and/or sound energy.
[0079] Hydrolyzable groups A, B, D, E, and F which may be employed
with advantage in silanes II and silanes III are halogen atoms,
especially chlorine, and/or alkoxy groups, such as methoxy, ethoxy,
n-propoxy, isopropoxy, n-butoxy, sec-butoxy or tert-butoxy groups.
Acetoxy groups are a further possibility for use. The additional
examples of hydrolyzable groups, known to the skilled worker, may
likewise be employed for the purposes of this invention.
[0080] The organic radicals B, C, D, E, and F which may be employed
in silanes II and silanes III include by way of example, with no
claim to completeness, methyl, ethyl, n-propyl, isopropyl, n-butyl,
sec-butyl, and tert-butyl groups, pentyl groups and also the
branched isomers, hexyl groups and also the branched isomers,
heptyl groups and also the branched isomers, octyl groups and also
the branched isomers, nonyl groups and also the branched isomers,
decyl groups and also the branched isomers, undecyl groups and also
the branched isomers, dodecyl groups and also the branched isomers,
tetradecyl groups and also the branched isomers, hexadecyl groups
and also the branched isomers, octadecyl groups and also the
branched isomers, and eicosyl groups and also the branched isomers.
The organic radicals of the invention may, furthermore, contain
cyclic and/or aromatic moieties. Representative structures are
cyclohexyl, phenyl, and benzyl groups. It is further in accordance
with the invention if as at least one organic radical use is made
of oligomers or polymers which contain at least one hydrolyzable
silyl group.
[0081] The organic radicals E, F, and G in which there is at least
one group X or Z which, during or after a coating operation, is
able to enter directly or after activation into a bond with the
polymer kind A and/or at least one group Y present in at least one
polymer kind A on exposure to thermal energy, electromagnetic
radiation, particulate radiation and/or sound energy include, for
example, the compounds compiled in the following list (the list
makes no claim to completeness): methyl, ethyl, n-propyl,
isopropyl, n-butyl, sec-butyl, and tert-butyl groups, pentyl groups
and also the branched isomers, hexyl groups and also the branched
isomers, heptyl groups and also the branched isomers, octyl groups
and also the branched isomers, nonyl groups and also the branched
isomers, decyl groups and also the branched isomers, undecyl groups
and also the branched isomers, dodecyl groups and also the branched
isomers, tetradecyl groups and also the branched isomers, hexadecyl
groups and also the branched isomers, octadecyl groups and also the
branched isomers, and eicosyl groups and also the branched isomers.
The organic radicals of the invention may, furthermore, contain
cyclic and/or aromatic moieties. Representative structures are
cyclohexyl, phenyl, and benzyl groups. It is further in accordance
with the invention if as at least one organic radical use is made
of oligomers or polymers which contain at least one hydrolyzable
silyl group. Where a radical from the above list is employed as one
or more of radicals E, F, and G, it is additionally modified by a
chemical moiety which contains at least one group Z or X.
[0082] Examples of silanes of structure II that can be used with
preference for the purposes of this invention are
methyltrimethoxysilane, methyltriethoxysilane,
dimethyldimethoxysilane, dimethyldiethoxysilane,
trimethylethoxysilane, ethyltrimethoxysilane,
propyltrimethoxysilane, propyltriethoxysilane,
isobutyltrimethoxysilane, isobutyltriethoxysilane,
octyltrimethoxysilane, octyltriethoxysilane,
isooctyltrimethoxysilane isooctyltriethoxysilane,
hexadecyltrimethoxysilane, hexadecyltriethoxysilane,
octadecylmethyldimethoxysilane, phenyltrimethoxysilane,
phenyltriethoxysilane, cyclohexylmethyldimethoxysilane,
dicyclo-pentyldimethoxysilane,
(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane and
(3,3,3-trifluoropropyl)trimethoxysilane.
[0083] An example of silyl-functionalized oligomers or polymers
which can be employed in accordance with the invention is
polyethylene glycol which has been linked with a trimethoxysilane
group.
[0084] Representatives of silanes of structure III which can be
used with particular preference for the purposes of this invention
and which carry at least one functionalization are, for example,
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,
N-(2-aminoethyl)-3-aminopropyl-triethoxysilane,
3-aminopropyltrimethoxysilane,
(3-trimethoxysilylpropyl)diethylenetriamine,
3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane,
N-(2-aminoethyl)-3-aminopropyldimethoxymethylsilane,
(N-butyl)-3-aminopropyltrimethoxysilane,
3-(N-ethylamino)-2-methylpropyltrimethoxysilane,
4-amino-3,3-dimethylbutyl-dimethoxymethylsilane,
(N-cyclohexyl)aminomethyldimethoxymethylsilane,
(N-cyclohexyl)-aminomethyltrimethoxysilane,
(N-phenyl)-3-aminopropyltrimethoxysilane,
(N-benzyl-2-aminoethyl)-3-aminopropyltrimethoxysilane
[2-(N-benzyl-N-vinylamino)ethyl]-3-aminopropyltrimethoxysilane
hydrogen chloride,
[2-(N-benzyl-N-vinylamino)ethyl]-3-aminopropyltrimethoxysilane,
bis(3-propyltriethoxysilyl)amine, aminophenyltrimethoxysilane
(meta- or para-), 2-(4-pyridylethyl)triethoxysilane,
N-(3-trimethoxysilylpropyl)pyrrole,
N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole,
2,2-dimethoxy-1,6-diaza-2-silacyclooctane,
N-allylaza-2,2-dimethoxysilacyclopentane,
3-ureidopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane,
isocyanatomethyltrimethoxysilane,
isocyanatomethyldimethoxymethylsilane,
tris[3-(trimethoxysilyl)propyl] isocyanurate,
6-azidosulfonylhexyltriethoxysilane, triethoxysilylpropyl
ethylcarbamate, (3-triethoxysilylpropyl) tert-butylcarbamate,
vinyltrimethoxysilane, vinyltriethoxysilane,
vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane,
vinyldimethoxymethylsilane, vinyltriacetoxysilane,
3-triethoxysilylpropylsuccinic anhydride,
3-glycidyloxy-propyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
3-glycidyloxy-propyldiethoxymethylsilane,
3-methacryloyloxypropyltriethoxysilane,
3-chloropropyltriethoxysilane,
bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane,
2-hydroxy-4-(3-triethoxysilylpropoxy)benzophenone,
4-(3'-chlorodimethylsilylpropoxy)benzophenone,
3-mercaptopropyltrimethoxysilane,
bis(3-triethoxysilylpropyl)disulfane,
bis(3-triethoxysilylpropyl)tetrasulfane,
bis(triethoxysilylpropyl)polysulfane, triethoxysilyl-butyraldehyde,
bisphenylphosphinoethyldimethylethoxysilane and
octadecylamine-dimethyltrimethoxysilylpropylammonium chloride.
[0085] Silanes which are disclosed in WO 00/43539 by Biochip
Technologies or in EP 281 941 B1 by Ciba Geigy, and those published
by Kolar et al. [A. Kolar, H. F. Gruber, G. Greber, JMS Pure Appl.
Chem., 1994, A31, 305-318], may likewise be employed for the
purposes of this invention as silanes of structure III. It is also
possible to use organic titanium and organic zirconium compounds,
optionally in conjunction with silanes.
[0086] The surface modification may take place completely by means
of at least one representative of the silanes III. It is also
possible, though, to use a combination of silanes III and silanes
II. Such a combination is inventive if at least 1% by weight,
preferably at least 5% by weight, of at least one representative of
the silanes III is used.
[0087] Silanes are used with particular preference for the purposes
of this invention as surface modifiers if filler particles are
employed which, at least in the state of the non-surface-modified
base unit, carry hydroxyl groups on the surface. Examples of this
kind of filler particles are metal oxides, especially amorphous
silicon dioxide. An exemplary possibility of realizing a surface
modification is given by Bauer and coworkers (F. Bauer, H. Ernst,
U. Decker, M. Findeisen, H.-J. Glasel, H. Langguth, E. Hartmann, R.
Mehnert, C. Peuker, Macromol. Chem. Phys., 2000, 201, 2654-2659]
and Rothon [R. N. Rothon (ed.), Particulate Filled Polymer
Composites, 2nd ed., 2003, Rapra Technology, Shawbury, pp.
153-206].
[0088] Particles which in the state of the non-surface-modified
base unit carry ionic groups on the surface can be modified
preferably using surfactants and/or fatty acids.
[0089] As surfactants it is possible in general to employ all
quaternary ammonium compounds, protonated amines, organic
phosphonium ions, and amino carboxylic acids that exhibit
amphiphilic behaviour. Advantageous use may be made of ammonium
compounds which carry at least three organic radicals, such as
alkylammonium salts, trimethylalkylammonium salts,
dimethyldialkylammonium salts, methylbenzyldialkylammonium salts,
dimethylbenzylalkylammonium salts or alkylpyridinium salts.
Furthermore, alkoxylated quaternary ammonium compounds may be
employed.
[0090] Two classes of surfactants may be distinguished for the
purposes of this invention: on the one hand, those which, in
addition to the groups capable of interaction with the base
surface, carry exclusively organic radicals which are chemically
inert (see structure IV); on the other, those which, in addition to
the groups capable of linking with the base surface, contain at
least one organic radical which carries at least one group X or Z
which, during or after a coating operation, is able to enter,
directly or after activation, into a bond with the polymer kind A
and/or at least one group Y present in at least one polymer kind A
on exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy (see structure V). In
surfactant IV the substituents A, B, and D may independently of one
another be organic radicals or hydrogen; the substituent C is a
long-chain organic radical. Any anions can be employed as
counterions. Examples are chloride, bromide, hydrogen sulphate,
dihydrogen phosphate, and tetrafluoroborate. The skilled worker is
aware of others which may likewise be employed for the purposes of
this invention. Independently of one another, the organic radicals
may be linear or branched, saturated or unsaturated, may be
composed of aliphatic, olefinic and/or aromatic elements, and may
contain 1 to 22 carbon atoms. Typical substituents used as organic
radicals include methyl groups, ethyl groups, n-propyl groups,
isopropyl groups, n-butyl groups, sec-butyl groups, tert-butyl
groups, linear or branched pentyl groups, linear or branched hexyl
groups, linear or branched heptyl groups, linear or branched octyl
groups, benzyl groups, or groups with higher numbers of carbon
atoms. Long-chain organic radicals employed include, preferably,
dodecyl groups, tetradecyl groups, hexadecyl groups, octadecyl
groups or eicosyl groups in saturated or unsaturated form. Since
the starting materials for surfactant manufacture are frequently
natural products, alkyl substituents with only one length of chain
are rarely encountered. Instead there is frequently a mixture of
alkyl chains different in length. Particularly preferred long-chain
organic radicals used are tallow radicals (unsaturated) or
hydrogenated tallow radicals (saturated). It is also in accordance
with the invention for the surfactant function to be taken on by
oligomers or polymers which have been functionalized such that they
carry at least one cationic group.
##STR00002##
[0091] Examples which may be used with preference for the purposes
of this invention as surfactants of structure IV are
hexadecyltrimethylammonium chloride or bromide,
methylditallowylammonium chloride or bromide, in which the tallow
radicals ("tallowyl") may be saturated or unsaturated,
dimethyltallowylbenzylammonium chloride or bromide, in which the
tallowyl radicals may be saturated or unsaturated,
dimethyltallowyl(2-ethylhexyl)ammonium chloride or bromide, in
which the tallowyl radicals may be saturated or unsaturated, and
dimethylditallowylammonium chloride or bromide, in which the
tallowyl radicals may be saturated or unsaturated.
[0092] Surfactants which are disclosed in EP 900 260 B1 by Akzo
Nobel, U.S. Pat. No. 5,739,087 by Southern Clay, U.S. Pat. No.
5,718,841 by Rheox, U.S. Pat. No. 4,141,841 by Procter &
Gamble, and by H Gro.beta.mann [H. Gro.beta.mann in Katalysatoren,
Tenside und Mineraloladditive, H. Falbe, U. Hasserodt (ed.), 1978.
G. Thieme, Stuttgart, p. 135ff] may likewise be employed for the
purposes of this invention as surfactants of structure IV.
[0093] Advantageous embodiments of surfactants of structure V that
are useful in accordance with the invention are those in which the
substituents E, F, and G independently of one another may be
organic radicals or hydrogen and the substituent C is a long-chain
organic radical. Any anions can be employed as counterions.
Examples are chloride, bromide, hydrogen sulphate, dihydrogen
phosphate, and tetrafluoroborate. Independently of one another, the
organic radicals may be linear or branched, saturated or
unsaturated, may be composed of aliphatic, olefinic and/or aromatic
elements, and may contain 1 to 22 carbon atoms. Typical
substituents used as organic radicals include methyl groups, ethyl
groups, n-propyl groups, isopropyl groups, n-butyl groups,
sec-butyl groups, tert-butyl groups, linear or branched pentyl
groups, linear or branched hexyl groups, linear or branched heptyl
groups, linear or branched octyl groups, benzyl groups, or groups
with higher numbers of carbon atoms. Long-chain organic radicals
employed include, preferably, dodecyl groups, tetradecyl groups,
hexadecyl groups, octadecyl groups or eicosyl groups in saturated
or unsaturated form. With regard to the starting materials for
manufacturing surfactant V as well, natural products are frequently
employed, so that rarely are alkyl substituents of a single chain
length present; instead, a mixture of alkyl chains of different
lengths is present. Particularly preferred long-chain organic
radicals used are tallow radicals (unsaturated) or hydrogenated
tallow radicals (saturated). It is also in accordance with the
invention for the surfactant function to be taken on by oligomers
or polymers which have been functionalized such that they carry at
least one cationic group. With regard to the surfactants V at least
one of substituents E, F, G, and C contains at least one group X or
Z which, during or after a coating operation, is able to enter,
directly or after activation, into a bond with the polymer kind A
and/or at least one group Y present in at least one polymer kind A
on exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy. Surfactants disclosed in
EP 900 260 B1 by Akzo Nobel, U.S. Pat. No. 5,739,087 by Southern
Clay, U.S. Pat. No. 5,718,841 by Rheox, U.S. Pat. No. 4,141,841 by
Procter & Gamble, and by H Gro.beta.mann [H. Gro.beta.mann in
Katalysatoren, Tenside und Mineraloladditive, H. Falbe, U.
Hasserodt (ed.), 1978. G. Thieme, Stuttgart, p. 135ff] may likewise
be employed for the purposes of this invention as surfactants of
structure V, provided they have been modified with at least one
group X or Z, in addition, under certain circumstances, to the
structure disclosed.
[0094] Examples which can be employed with preference for the
purposes of this invention as surfactants of structure V are
methyltallowyldi(2-hydroxyethyl)ammonium chloride or bromide,
allyldimethyltetradecyl chloride or bromide,
allyidimethylhexadecylammonium chloride or bromide, and
allyldimethyloctadecylammonium chloride or bromide.
[0095] For the purposes of this invention it is possible with
preference to use a combination of surfactants IV and surfactants
V. In this embodiment of the invention, representatives of
surfactants V are present at a level of at least 1% by weight,
preferably at least 5% by weight, among all of the surfactants
employed. Furthermore, it is possible to use surfactants IV or V in
combination with cationic compounds which, though not themselves
surfactants, carry at least one group X or Z which is able, during
or after a coating operation, to enter, directly or after
activation, into a bond with the polymer kind A and/or at least one
group Y present in at least one polymer kind A on exposure to
thermal energy, electromagnetic radiation, particulate radiation
and/or sound energy. At least 1% by weight, preferably at least 5%
by weight, of a cationic compound of this kind is used in
accordance with the invention in combination with surfactants IV
and/or V. Where cationic compounds of this kind are employed, the
sum of surfactants IV and V employed is not more than 99% by
weight, preferably not more than 95% by weight, it being possible
for surfactants V to be replaced entirely by surfactants IV.
Examples of such cationic compounds are
(2-acryloyloxyethyl)(4-benzoylbenzyl)dimethylammonium chloride or
bromide, 3-trimethylammoniopropyl-methacrylamide chloride or
bromide, 2-trimethylammmonioethyl methacrylate chloride or bromide,
3-dimethylalkylammoniopropylmethacrylamide chloride or bromide, and
2-dimethyl-alkylammoniomethyl methacrylate chloride or bromide.
[0096] Surfactants are used with particular preference for the
purposes of this invention if the filler particles employed have
negative charges or partial charges on the surface (in the state of
the non-surface-modified base unit). Examples of this kind of
filler particles are certain clay minerals, particularly smectites,
in which intercalated cations may be replaced by surfactants. One
principle whereby such replacement may take place has been
formulated by Lagaly [G. Lagaly in Tonminerale und Tone, K.
Jasmund, G. Lagaly (ed.), 1993, Steinkopff, Darmstadt, p.
366ff].
[0097] It is possible, furthermore, to use combinations of
inventive silanes and inventive surfactants. At least one of the
surface modification reagents employed contains at least one group
Z, which decomposes or is chemically transformed into group X by
thermal energy, electromagnetic radiation, particulate radiation
and/or sound energy, which, during or after a coating operation, is
able to enter directly into a bond with the polymer kind A and/or
at least one group Y present in the polymer kind A on exposure to
thermal energy, electromagnetic radiation, particulate radiation
and/or sound energy alike, the activation temperature being equal
to or above the processing temperature in the case of thermal
activation of group Z as well as the crosslinking reaction of group
X.
Further Constituents
[0098] It is additionally in accordance with the invention to use,
optionally, polymers C containing at least one group of type Z,
and/or polymers C containing at least one group Z and at least one
group of type X, and/or polymers C containing at least one group Z
and at least one group of type X and type Y and/or polymers C
containing neither type-Z or -X nor type-Y groups. The composition
of those polymers, employable optionally, that contain no groups of
type X, Y or Z are subject to the same details in terms of
construction, composition, choice of monomers, softening
temperature, and structure as contained in the definition of the
polymers A, apart from the details given there in respect of groups
Y. Optionally employable polymers containing at least one group Z
and/or X are subject to the details given for polymers A, but such
polymers C contain groups of kind Z and/or X and not groups of kind
Y and can therefore, during or after a coating operation, enter,
directly or by activation, into a bond with the polymer kind A
and/or at least one group Y of the at least one polymer of kind A
by exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy. The incorporation of
groups Z and/or X into polymers C is subject to the same details
given for groups Y in the polymers A. Where polymers are employed
that carry groups Z and/or X and Y, then the same details, in terms
of construction, composition, choice of monomers, softening
temperature, and structure, apply as contained in the definition of
the polymers A, but with the addition that there is also at least
one group Z and/or X present in the polymer. For the incorporation
of groups Z and/or X and Y into polymers C which carry both kinds
of groups, the details which apply are the same as those given for
the groups Y in the polymers A.
[0099] As further constituents the PSA formulations of the
invention may comprise tackifier resins, plasticizers, rheological
additives, catalysts, initiators, stabilizers, compatibilizers,
coupling reagents, crosslinkers, antioxidants, other aging
inhibitors, light stabilizers, flame retardants, pigments, dyes,
further fillers, especially those not included in at least one
filler particle kind B, and/or expandants.
Combinations of Groups X and Y
[0100] The PSAs of the invention comprise at least one polymer kind
A and at least one filler particle kind B. Polymers A contain at
least two groups Y; filler particles B contain at least one kind of
groups Z, which decomposes or is chemically transformed into group
X by thermal energy, electromagnetic radiation, particulate
radiation and/or sound energy. Groups X, Y and Z are chosen for the
purposes of this invention such that between these groups X and Y
or by way of these groups X and Y it is possible to bring about
coupling between polymers A and filler particles B, whereas, in
turn, no coupling is brought about between polymers A and filler
particles B between groups Z and Y or by way of groups Z and Y. The
coupling is initiated during or after the coating operation by
exposure to thermal energy, electromagnetic radiation, particulate
radiation and/or sound energy. The coupling involves at least one
group X and at least one group Y. By coupling of at least one group
X and at least one group Y is meant for the purposes of this
invention, in particular [0101] a chemical reaction in which the at
least one group X reacts with the at least one group Y and leads to
the formation of a covalent bond, [0102] the formation of hydrogen
bonds between the at least one group X and the at least one group
Y, and/or [0103] the formation of a coordinative bond as a result,
for example, of formation of a complex, involving the at least one
group X and the at least one group Y, so that at least one
donor/acceptor bond is formed.
[0104] The coupling in this case may take place between the groups
X and Y directly or else by mediation through one or more further
substances, such as coupling reagents or crosslinkers. The position
and number of groups X and Y in the polymers A and filler particles
B that can be used in accordance with the invention are subject to
the same definitions given for the polymers A and the filler
particles B.
[0105] Where the coupling of the invention between the at least one
polymer kind A and the at least one filler particle kind B is to
proceed via the groups Y and X as a chemical reaction, the groups X
and Y involved are defined in particular in accordance with the
following remarks.
[0106] The PSAs of the invention comprise at least one constituent
which comprises at least one kind of inventive segments having the
general structure (R.sup.oR.sup.ooR.sup.oooC)-Z. R.sup.o, R.sup.oo
and R.sup.ooo may independently of one another be saturated or
unsaturated, aliphatic or aromatic hydrocarbon radicals which may
also be linked to one another and may be identical or different.
For the purposes of this invention it is also possible for the
carbon atom in (R.sup.oR.sup.ooR.sup.oooC)-Z itself to be
unsaturated. In that case said carbon atom is linked only to Z and
to one or two of the radicals R.sup.o, R.sup.oo or R.sup.ooo. The
group Z per se is not capable of coupling with the at least one
polymer kind A, and must first be converted or made to decompose
through exposure to thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy, to form the group X,
thus resulting in the structure (R.sup.oR.sup.ooR.sup.oooC)--X. The
radicals R.sup.o, R.sup.oo, and R.sup.ooo may independently of one
another include any number of heteroatoms. The radicals R.sup.o,
R.sup.oo, and R.sup.ooo may be of low molecular mass or may be
polymeric in nature. Up to two of the radicals R.sup.o, R.sup.oo,
and R.sup.ooo may also be hydrogen atoms, moreover. At least one of
the radicals R.sup.o, R.sup.oo, and R.sup.ooo is linked by a
chemical or ionic bond, by chemisorption or physisorption, to a
filler particle of kind B. The group needed for the coupling
reaction is designated X.
[0107] The at least one inventive segment of structure
(R.sup.oR.sup.ooR.sup.oooC)--X can be reacted with at least one
segment which is present in at least one further constituent of the
PSA of the invention and which has the general structure
(R*R**R***C)--Y. R*, R** and R*** may independently of one another
be saturated or unsaturated, aliphatic or aromatic hydrocarbon
radicals which may also be linked to one another and may be
identical or different. For the purposes of this invention it is
also possible for the carbon atom in (R*R**R***C)--Y itself to be
unsaturated. In that case said carbon atom is linked only to Y and
to one or two of the radicals R*, R** or R***. The radicals R*,
R**, and R*** may independently of one another include any number
of heteroatoms. The radicals R*, R**, and R*** may be of low
molecular mass or may be polymeric in nature. Up to two of the
radicals R*, R**, and R*** may also be hydrogen atoms, moreover. At
least one of the radicals R*, R**, and R*** is linked by a chemical
bond, to a polymer chain of kind A. The group needed for the
coupling reaction is designated Y. In specific versions of this
invention, single or plural radicals R*, R** or R*** may be of the
same identity as R.sup.o, R.sup.oo or R.sup.ooo. It is also in
accordance with the invention if group X and group Y are identical.
In this specific case the coupling takes place advantageously by
means of a coupling reagent or by the action of a catalyst or
initiator. For the purposes of this invention it is particularly
advantageous if the coupling reaction is initiated by exposure to
thermal energy, however it can also be initiated exclusively or by
combination with electromagnetic radiation, particulate radiation
and/or sound energy.
[0108] For the purposes of this invention it is possible to use an
arbitrarily large number of further groups, which may react with a
group X and/or with a group Y.
[0109] A coupling reaction may proceed by chemical reaction
directly between the groups X and Y, so forming a species
(R.sup.oR.sup.ooR.sup.oooC)--X'--Y'-(CR*R**R***) (see FIG. 2). In
the case of a chemical reaction, X' and Y' are the reaction
products of the groups X and Y respectively. In specific cases the
coupling of groups X and Y requires a coupling reagent
X.sup.a--Y.sup.a or X.sup.a--R.sup.a--Y.sup.a. X.sup.a and Y.sup.a
are groups capable of reaction with groups X and Y, respectively,
and may be identical or different. It is also possible,
furthermore, to link two groups X via coupling reagent
Y--R.sup.b--Y and also two groups Y via a coupling reagent
X--R.sup.b--X. R.sup.a and R.sup.b can be saturated or unsaturated,
aliphatic or aromatic hydrocarbon radicals and may contain an
arbitrary number of heteroatoms. The radicals R.sup.a and R.sup.b
may be of low molecular mass or may be polymeric in nature.
[0110] Table 1 gives a number of examples of the groups Z and also
of the groups X which originate from them by means of thermal
energy, electromagnetic radiation, particulate radiation and/or
sound energy. The table makes no claim to completeness, but is
instead merely intended to give examples of protective groups Z for
the groups X that can be used in the context of this invention.
Further groups known to the skilled worker may likewise be employed
in accordance with the invention [see: T. W. Greene, P. G. M. Wuts;
Protective Groups in Organic Synthesis, 3rd Edition, John Wiley
& Sons, Inc; New York, 1999].
[0111] Table 2 lists a number of examples of X and Y which can be
used in accordance with the invention. Combinations of groups which
can be used with advantage are marked with a cross. In certain
circumstances, additional reagents and/or special conditions are
needed for the reaction between the groups indicated. Reagents of
this kind are then added to the PSA formulation (see "Further
constituents" section). Specific conditions such as temperature or
radiation also come within the intention of this invention. The
table does not make any claim to completeness, but is intended
merely to indicate examples of groups which can be employed for the
purposes of this invention, and combinations of groups that can be
employed. Further groups and combinations, known to the skilled
worker, for corresponding reactions may likewise be employed in
accordance with the invention. The radicals R.sup.1, R.sup.2,
R.sup.3, R.sup.4, R.sup.5, and R.sup.6 and also R.sup.a, R.sup.b,
R.sup.c, R.sup.d, R.sup.e and R.sup.f in Table 1 may independently
of one another be saturated or unsaturated, aliphatic or aromatic
hydrocarbon radicals, which may contain any number of heteroatoms
and may be of low molecular mass or may be polymeric in nature,
and/or, alternatively, may be hydrogen atoms. In accordance with
the definition above, the radicals may be identical or different in
construction. The radicals R.sup.1, R.sup.2, and R.sup.3 may be
linked to one another, the radicals R.sup.5 and R.sup.6 may be
linked to one another, the radicals R.sup.a, R.sup.b, and R.sup.c
may be linked to one another, and the radicals R.sup.e and R.sup.f
may be linked to one another. Cyclic acid anhydrides such as maleic
anhydride or succinic anhydride may be attached arbitrarily as a
chemical group to polymers A or filler particles B. Maleic
anhydride offers the possibility, furthermore, of being
incorporated as a comonomer in polymers A.
[0112] The entry "-PI" in Table 1 refers to a group which is
possessed of a photoinitiator function. Irradiation with UV light
of appropriate wavelength activates the group and, depending on the
nature of the photoinitiator, a free-radical reaction or a cationic
reaction is initiated. Suitable representatives of such groups are
type-I photoinitiators, in other words .alpha.-cleaving initiators
such as benzoin derivatives and acetophenone derivatives, benzil
ketals or acylphosphine oxides, type-II photoinitiators, in other
words hydrogen abstractors such as benzophenone derivatives and
certain quinones, diketones and thioxanthones, and cationic
photoinitiators, such as "photoacid generators" such as arylated
sulfonium or iodonium salts and dimerized arylated imidazole
derivatives. Further, triazine derivatives can be used to initiate
free-radical and cationic reactions.
[0113] Photoinitiating groups Z and/or X and/or Y of type I include
for the purposes of this invention, preferably, benzoin, benzoin
ethers such as, for example, benzoin methyl ether, benzoin
isopropyl ether, benzoin butyl ether, benzoin isobutyl ether,
methylolbenzoin derivatives such as methylolbenzoin propyl ether,
4-benzoyl-1,3-dioxolane and its derivatives, benzil ketal
derivatives such as 2,2-dimethoxy-2-phenylacetophenone or
2-benzol-2-phenyl-1,3-dioxolane,
.alpha.,.alpha.-dialkoxyacetophenones such as
.alpha.,.alpha.-dimethoxyacetophenone and
.alpha.,.alpha.-diethoxyactophenone, .alpha.-hydroxyalkyl phenones
such as 1-hydroxycyclohexyl phenyl ketone,
2-hydroxy-2-methyl-1-phenylpropanone and
2-hydroxy-2-methyl-1-(4-isopropylphenyl)propanone,
4-(2-hydroxyethoxy)phenyl-2-hydroxy-2-methyl-2-propanone and its
derivatives, .alpha.-aminoalkylphenones such as
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-2-one and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one,
acylphosphine oxides such as
2,4,6-trimethylbenzoyldiphenylphosphine oxide and
ethyl-2,4,6-trimethylbenzoylphenylphosphinate, and
O-acyl-.alpha.-oximino ketones.
[0114] Photoinitiating groups of type II that can be used with
preference in accordance with the invention are based for example
on benzophenone and its derivatives such as
2,4,6-trimethylbenzophenone or 4,4'-bis(dimethylamino)benzophenone,
thioxanthone and its derivatives such as 2-isopropylthioxanthone
and 2,4-diethylthioxanthone, xanthone and its derivatives, and
anthraquinone and its derivatives.
[0115] Type-II photoinitiators are used with particular advantage
in combination with nitrogen-containing coinitiators, known as
amine synergists. For the purposes of this invention it is
preferred to use tertiary amines. Furthermore, in combination with
type-II photoinitiators, hydrogen atom donors are employed
advantageously. Examples thereof are substrates which contain amino
groups. Examples of amine synergists are methyldiethanolamine,
triethanolamine, ethyl 4-(dimethylamino)benzoate, 2-n-butoxyethyl
4-(dimethylamino)-benzoate, isoacryl 4-(dimethylamino)benzoate,
2-(dimethylaminophenyl)ethanone, and also unsaturated tertiary
amines copolymerizable therewith, (meth)acrylated amines,
unsaturated, amine-modified oligomers and polymers based on
polyester or polyether, and amine-modified (meth)acrylates. For the
purposes of this invention it is possible for such chemical
assemblies to be linked to polymers and/or fillers.
[0116] For the purposes of this invention it is also possible to
use any desired combinations of different varieties of type-I
and/or type-II photoinitiating groups.
[0117] In one particularly preferred version of this invention,
groups of photoinitiating character are present as groups Y in at
least one kind of polymers A.
[0118] In a further particularly preferred version of this
invention, groups of photoinitiating character are present as
groups Z and/or X in at least one kind of functionalized filler
particles B.
[0119] When the coupling of the invention between the at least one
polymer kind A and the at least one filler particle kind B proceeds
via the groups Y and X by way of the formation of hydrogen bonds,
the groups X and Y involved are defined in accordance with the
following remarks. In this regard see, for example, D. Philp, J. F.
Stoddard, Angew. Chem., 1996, 108, 1242-1286 or C. Schmuck, W.
Wienand, Angew. Chem., 2001, 113, 4493-4499.
[0120] The PSAs of the invention comprise in this case at least one
constituent which comprises one kind of segments having the general
structure (R.sup.#R.sup.##R.sup.###C)--X.sup.#. R.sup.#, R.sup.##
and R.sup.### may independently of one another be saturated or
unsaturated, aliphatic or aromatic hydrocarbon radicals which may
also be linked to one another and may be identical or different.
For the purposes of this invention it is also possible for the
carbon atom in (R.sup.#R.sup.##R.sup.###C)--X.sup.# itself to be
unsaturated. In that case said carbon atom is linked only to
X.sup.# and to one or two of the radicals R.sup.#, R.sup.## or
R.sup.###. The radicals R.sup.#, R.sup.##, and R.sup.### may
independently of one another include any number of heteroatoms. The
radicals R.sup.#, R.sup.##, and R.sup.### may be of low molecular
mass or may be polymeric in nature. Up to two of the radicals
R.sup.#, R.sup.##, and R.sup.### may also be hydrogen atoms,
moreover. At least one of the radicals R.sup.#, R.sup.##, and
R.sup.### is linked by a chemical or ionic bond, by chemisorption
or physisorption, to a filler particle of kind B. The group needed
for the coupling reaction is designated X.sup.#, which in turn
originates by means of thermal energy, electromagnetic radiation,
particulate radiation and/or sound energy from a group Z. The group
Z in turn is either not capable of coupling the at least one
polymer kind A to the at least one filler particle B through
formation of hydrogen bonds, or may likewise exhibit such
interactions, which, however, owing to polyvalence effects or
chelation, however, are not so strongly pronounced as in the case
of the group X.sup.#.
[0121] The at least one inventive segment of structure
(R.sup.#R.sup.##R.sup.###C)--X.sup.# is able to form hydrogen bonds
with at least one functional segment which is present in at least
one further constituent and which has the general structure
(R.sup..about.R.sup..about..about.R.sup..about..about..about.C)--Y.sup..a-
bout.. R.sup..about., R.sup..about..about. and
R.sup..about..about..about. may independently of one another be
saturated or unsaturated, aliphatic or aromatic hydrocarbon
radicals which may also be linked to one another and may be
identical or different. For the purposes of this invention it is
also possible for the carbon atom in
(R.sup..about.R.sup..about..about.R.sup..about..about..about.C)--Y.sup..a-
bout. itself to be unsaturated. In that case said carbon atom is
linked only to Y.sup..about. and to one or two of the radicals
R.sup..about., R.sup..about..about. or R.sup..about..about..about..
The radicals R.sup..about., R.sup..about..about., and
R.sup..about..about..about. may independently of one another
include any number of heteroatoms. The radicals R.sup..about.
R.sup..about..about., and R.sup..about..about..about. may be of low
molecular mass or may be polymeric in nature. Up to two of the
radicals R.sup..about., R.sup..about..about., and
R.sup..about..about..about. may also be hydrogen atoms, moreover.
At least one of the radicals R.sup..about., R.sup..about..about.,
and R.sup..about..about..about. is linked by a chemical bond, to a
polymer chain of kind A. The group needed for the coupling reaction
is designated Y.sup..about.. In specific versions of this
invention, single or plural radicals R.sup..about.,
R.sup..about..about., and R.sup..about..about..about. may be of the
same identity as R.sup.#, R.sup.## or R.sup.###. It is also in
accordance with the invention if group X.sup.# and group
Y.sup..about. are identical. In this specific case the coupling
takes place by means of a coupling reagent.
[0122] For the purposes of this invention it is possible to use an
arbitrarily large number of further groups, which may enter into a
bond with at least one group X and/or at least one group Y.
[0123] A coupling reaction may proceed by formation of hydrogen
bonds directly between the groups X.sup.# and Y.sup.# so forming a
species
(R.sup.#R.sup.##R.sup.###C)--X.sup.#-Y.sup..about.--(CR.sup..about.R.sup.-
.about..about.R.sup..about..about..about.) (see FIG. 2). In
specific cases the coupling of groups X.sup.# and Y.sup..about.
requires a coupling reagent X.sup.#a--Y.sup..about.a or
X.sup.#a--R.sup.a'--Y.sup..about.a. X.sup.#a and Y.sup..about.a are
groups capable of forming hydrogen bridges with groups X.sup.# and
Y.sup..about., respectively, and may be identical or different. It
is also possible, furthermore, to link two groups X.sup.# via
coupling reagent Y.sup..about.--R.sup.b'--Y.sup..about. and also
two groups Y.sup..about. via a coupling reagent
X.sup..about.--R.sup.b'--X.sup..about.. R.sup.a' and R.sup.b' can
be saturated or unsaturated, aliphatic or aromatic hydrocarbon
radicals and may contain an arbitrary number of heteroatoms. The
radicals R.sup.a' and R.sup.b' may be of low molecular mass or may
be polymeric in nature.
[0124] The coupleable groups may be unidentate or, preferably
multidentate. Denticity refers in this case to the capacity of a
group to form a certain number of hydrogen bonds. Hydrogen bonds
between unidentate or, preferably, multidentate functional
segments, as structure-forming elements, are known from a variety
of examples. In nature, hydrogen bonds between complementary
functional segments are used for the construction of
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). A specific
combination of donor and acceptor sites makes it possible for
couplings to be able to take place only in accordance with the
lock-and-key principle. Where, for example, the functional segments
.alpha. ("key" type) and .beta. ("lock" type) are complementary
segments which are able to form hydrogen bonds, then a compound is
possible between .alpha. and .beta. but not between .alpha. and
.alpha. or between .beta. and .beta.. With regard to the selection
of the functional segments, nature, when constructing DNA,
restricts itself to the two organic base pairs adenine/thymine (or
uracil instead of thymine in RNA) as bidentate segments and
cytosine/guanine as tridentate segments.
[0125] For the purposes of this invention it is possible to use
polymers A and filler particles B having groups based on adenine,
thymine, uracil, cytosine, guanine, derivatives thereof, and also
further compounds capable of forming hydrogen bonds by the
lock-and-key principle, such as, for example, 2-ureido-4-pyrimidone
and its derivatives, 2,6-diacetylaminopyridine and its derivatives,
diacetylpyrimidine and its derivatives, and ureidoacylpyrimidine
and its derivatives. This listing makes no claim to completeness.
Instead, the skilled worker is aware of further systems which can
be used in accordance with the invention. When this kind of
functionalization is chosen, then, for the purposes of this
invention, either the at least one polymer kind A carries groups of
the "key" type and the at least one filler particle B carries
groups of the "lock" type, or vice versa. FIG. 4 shows two examples
of the coupling of reactive constituents via formation of hydrogen
bonds, by using two complementary groups; on the one hand, the
direct coupling of polymer A and filler particle B, and, on the
other, the coupling of polymer A and filler particle B using a
coupling reagent ("key lock principle").
[0126] Likewise possible in accordance with the invention is the
coupling of groups via coordinate bonds. Examples of coordinate
bonds are ligand-central atom bonds in complexes, i.e., the
formation of a coordinate bond with metal atoms which may be
present in elemental form, in the form of metal salts and/or in the
form of metal complexes, and also all other donor-acceptor bonds
(in this regard see, for example, D. Philp, J. F. Stoddard, Angew.
Chem., 1996, 108, 1242-1286; M. Rehahn, Acta Polym., 1998, 49,
201-224 or B. G. G. Lohmeijer, U.S. Schubert, J. Polym. Sci. A
Polym. Chem., 2003, 41, 1413-1427).
[0127] If this coupling principle is chosen for the purposes of
this invention, then the PSA comprises filler particles of kind B
which contain groups having the general structure
(R.sup..sctn.R.sup..sctn..sctn.R.sup..sctn..sctn..sctn.C)-X.sup..sctn..
R.sup..sctn., R.sup..sctn..sctn. and R.sup..sctn..sctn..sctn. may
independently of one another be saturated or unsaturated, aliphatic
or aromatic hydrocarbon radicals which may also be linked to one
another and may be identical or different. For the purposes of this
invention it is also possible for the carbon atom in
(R.sup..sctn.R.sup..sctn..sctn.R.sup..sctn..sctn..sctn.C)--X.sup..sctn.
itself to be unsaturated. In that case said carbon atom is linked
only to X.sup..sctn. and to one or two of the radicals
R.sup..sctn., R.sup..sctn..sctn. or R.sup..sctn..sctn..sctn.. The
radicals R.sup..sctn., R.sup..sctn..sctn., and
R.sup..sctn..sctn..sctn. may independently of one another include
any number of heteroatoms. The radicals R.sup..sctn.,
R.sup..sctn..sctn., and R.sup..sctn..sctn..sctn. may be of low
molecular mass or may be polymeric in nature. Up to two of the
radicals R.sup..sctn., R.sup..sctn..sctn., and
R.sup..sctn..sctn..sctn. may also be hydrogen atoms, moreover. At
least one of the radicals R.sup..sctn., R.sup..sctn..sctn., and
R.sup..sctn..sctn..sctn. is linked by a chemical or ionic bond, by
chemisorption or physisorption, to a filler particle of kind B. The
group needed for the coupling reaction is designated X.sup..sctn.,
which in turn originates by means of thermal energy,
electromagnetic radiation, particulate radiation and/or sound
energy from a group Z. The group Z, again, either is not capable of
coupling the at least one polymer kind A to the at least one filler
particle B through formation of a coordinate bond, or may likewise
exhibit such bonds, which, however, owing to polyvalence effects or
chelation, for example, are not as strong as those of the group
X.sup..sctn., meaning that the polymer, up until the time of
conversion of the group Z into the group X.sup..sctn., also remains
readily processable, and in one preferred embodiment processable
from the melt. At the same time the PSA comprises polymers of kind
A which contain groups having the general structure
(R.sup.=R.sup.==R.sup.===C)--Y.sup.=. R.sup.=, R.sup.== and
R.sup.=== may independently of one another be saturated or
unsaturated, aliphatic or aromatic hydrocarbon radicals which may
also be linked to one another and may be identical or different.
For the purposes of this invention it is also possible for the
carbon atom in (R.sup.=R.sup.==R.sup.===C)--Y.sup.= itself to be
unsaturated. In that case said carbon atom is linked only to
Y.sup.= and to one or two of the radicals R.sup.=, R.sup.== or
R.sup.===. The radicals R.sup.=, R.sup.==, and R.sup.=== may
independently of one another include any number of heteroatoms. The
radicals R.sup.=, R.sup.==, and R.sup.=== may be of low molecular
mass or may be polymeric in nature. Up to two of the radicals
R.sup.=, R.sup.==, and R.sup.=== may also be hydrogen atoms,
moreover. At least one of the radicals R.sup.=, R.sup.==, and
R.sup.=== is linked by a chemical bond, to a polymer chain of kind
A. The group needed for the coupling reaction is designated
Y.sup.=. The groups X5 and Y.sup.= may be identical or different.
If they are different, then one of the varieties of groups takes on
the donor function and the other the acceptor function that are
necessary for the formation of coordinate bonds. If both groups are
of the same kind, then the coordinate bond is formed by way of a
coupling reagent.
[0128] The groups in the polymers A and filler particles B are
advantageously constructed such that they are capable of being able
to form coordinate bonds with metals of type M, which may be in
elemental form, in metal salt form or in the form of metal
complexes. Metal complexes may also be polynuclear. Unidentate or
multidentate segments may be employed. The coupling principle is
depicted diagrammatically in FIG. 5. At least two groups of the
"key" type couple by coordination of M, which takes on the "lock"
function. During the formation of the coordinate bond ("coupling"),
the structure of M may alter to become M'. This may be manifested
in altered oxidation states or else in an altered ligand structure
and/or ligand composition. When using metal atoms it is
particularly advantageous for the purposes of this invention to
take special precautions to disperse M in the PSA. This is
preferably accomplished by choosing particularly suitable
counterions, in the case of metal salts, or particularly suitable
complex ligands, in the case of metal complexes. Suitable
counterions and complex ligands therefore take on the function of
compatibilizers and dispersing assistants. It is particularly
advantageous to disperse the metal atom M in a meltable matrix that
contains no constituents able to enter into coordinate bonds with
M. This mixture is metered into the rest of the PSA formulation,
comprising at least one polymer kind A and at least one filler
particle kind B, not until immediately before the coating
operation.
[0129] Particular preference is given to coupling using chelating
segments. Examples of ligands which may be employed as groups are
bipyridine and terpyridine and also their derivatives,
acetylacetonate and its derivatives, ethylenediaminetetraacetic
acid and its derivatives, nitrilotriacetic acid and its
derivatives, hydroxyethylethylenediaminetriacetic acid and its
derivatives, diethylenetriaminepentaacetic acid and its
derivatives, and carboxylic acids. This listing makes no claim to
completeness. Instead, the skilled worker will be aware of further
systems which may be used in accordance with the invention. These
groups are not reactive with one another. All constituents
containing these groups can therefore be used in one mass stream.
The coupling of the groups takes place as soon as the mixture
comprising metal atom M is admixed to the mass stream, which for
the purposes of this invention takes place immediately prior to the
coating operation.
[0130] Suitable metal atoms for the purposes of this invention are
all those chemical elements capable of acting as an acceptor for
coordinate bonds. These are alkaline earth metals, preferably Ca
and/or Mg, transition metals, preferably Ti, Mn, Fe, Co, Ni, Cu,
Zn, Mo, Ru, Rh, Pd, W, Re, Os, Ir and/or Pt, and also Al and
lanthanoids. Examples of suitable compatibilizers and dispersing
assistants for these metal atoms which can be used in accordance
with the invention are alkoxides of aliphatic or aromatic,
saturated or unsaturated molecules containing any desired number of
heteroatoms, it being possible for these molecules to be of low
molecular mass or to be polymeric in nature. Additionally suitable
are open-chain or cyclic unsaturated hydrocarbons which contain any
number of heteroatoms and may be of low molecular mass or may be
polymeric in nature. Further dispersing assistants and
compatibilizers for M, useful in accordance with the invention, are
low molecular mass chelating compounds of organic identity.
[0131] Generally speaking, M can be an acceptor group ("key") which
in conjunction with a donor group of the "lock" type is able to
form a coordinate bond. In this case the acceptor group may be
attached to polymer A and filler particle B or else may be used in
the form of coupling reagents. This general case is depicted
diagrammatically in FIG. 6. It is further in accordance with the
invention to use filler particles B and polymers A furnished with
acceptor groups in combination with coupling reagents which carry
donor groups.
[0132] For the purposes of this invention it is possible for any
desired combinations of different sorts of coupling reactions to be
employed. In accordance with the invention at least one kind of
coupling reaction is used.
Methods of Producing Self-Adhesive Products
[0133] The production of self-adhesive products of the invention
embraces the operating steps of formulating/compounding, of
coating, and of crosslinking.
Compounding Methods
[0134] The formulations of the invention can be produced using
solvents in stirred tanks or, for example, in solvent kneading
apparatus or else by using high-speed dispersers. Preferably,
however, formulations of this kind are produced solventlessly.
Appropriate for this purpose are kneading apparatus, in batch
operation, and extruders, such as twin-screw extruders, in
continuous operation. Suitable compounding units for the purposes
of this invention are those which contain dispersive and,
optionally, distributive mixing elements. Dispersive mixing
elements ensure very fine distribution of the filler particles in
the formulation, while the distributive elements homogenize melted
constituents such as resins or polymers in the mixture of the PSA
formulation. Particularly appropriate in solventless batch
operation are Banbury mixers and also kneading apparatus of Buss or
Baker-Perkins type. In continuous operation, twin-screw extruders
in corotating mode can be used with preference.
Coating Methods
[0135] Coating methods which can be employed for the purposes of
this invention include knife coating methods, nozzle knife coating
methods, rolling rod nozzle methods, extrusion nozzle methods,
casting nozzle methods, and caster methods. Likewise in accordance
with the invention are application methods such as roll application
methods, printing methods, screen-printing methods, patterned roll
methods, ink-jet methods, and spraying methods. For the feeding of
the coating unit of the invention it is possible as an option to
include a conveying and/or mixing assembly, e.g., a single-screw or
twin-screw extruder, between metering system and mixing system. The
extruder which can be used alternatively is separately heatable. A
further drying step is combined with the coating at least in the
case of solvent-containing mass systems.
Crosslinking Methods
[0136] It is particularly preferred to initiate the crosslinking of
the PSA following the operation of applying it by coating.
Advantageous for this purpose is a radiation process. One very
preferred variant that may be mentioned, and that be used for the
purposes of this invention, is that of crosslinking with
ultraviolet radiation. By means of brief exposure to light in a
wavelength range between 200 to 400 nm, the coated material, which
in this version of the invention contains the photoinitiator
functions preferably as groups X and/or groups Y, is irradiated and
hence crosslinked. Employed in particular for this purpose are
high-pressure or medium-pressure mercury lamps at a power of 80 to
240 W/cm. Other radiation sources which can be used for the
purposes of this invention are those familiar to the skilled
worker. Alternatively, the emission spectrum of the lamp is adapted
to the photoinitiator used, or the type of photoinitiator is
adapted to the lamp's spectrum. The intensity of irradiation is
adapted to the respective quantum yield of the UV photoinitiator,
to the degree of crosslinking that is to be set, and to the web
speed.
[0137] Furthermore, it is possible with preference to crosslink the
PSA formulations of the invention with electron beams after they
have been applied by coating. This may also take place in
combination with a UV crosslinking operation. Typical irradiation
equipment that may be employed includes linear cathode systems,
scanner systems, and segmented cathode systems where electron beam
accelerators are concerned. Typical acceleration voltages are
situated in the range between 50 kV and 1 MV, preferably between 80
kV and 300 kV. The radiation doses employed are situated between 5
to 250 kGy, in particular between 20 and 100 kGy.
[0138] In one further advantageous embodiment the initiation of the
crosslinking reaction is by means of sound energy, such as
ultrasound, for example, the group Z undergoing decomposition to
form the group X, which only then is capable of reaction with the
at least one polymer of kind A or with the group Y which is
attached to the at least one polymer of kind A. In one particularly
advantageous version of this variant the initiation takes place, in
the case both of the batchwise regime and of the continuous regime,
either between the compounding step and the coating operation, or
after the coating, in order to ensure that the composition can be
processed specifically in the context of a solvent-free operating
regime. The sound energy is generated by direct sonication horns.
Further sound sources which can be employed for the purposes of
this invention are the sound sources familiar to the skilled
worker. The actual crosslinking takes place after the activation by
means of sound energy, and takes place thermally. The thermal
energy for the crosslinking reaction is in that case either taken
from the preheated flows of composition, made available by the
setting of a temperature on the coating assembly, or realized via a
heating tunnel or infrared section after the coating. It is
likewise possible in accordance with the invention to utilize the
thermal energy that is released in one or more exothermic reactions
for the process of this thermal reaction. Combinations of these
process possibilities, especially with the radiation-chemical
crosslinking processes, are possible in the context of this
invention.
[0139] Use is made typically of direct sonication horns whose
powers are in the range between 50 W and 16 kW, preferably 1 kW and
16 kW. The frequencies employed are between 20 kHz to 2 MHz, more
particularly between 20 and 30 kHz.
[0140] For the purposes of this invention it is additionally
particularly preferable to realize the crosslinking by exposure to
thermal energy. This can be done optionally in combination with one
or more radiation methods. Where thermal energy is used to initiate
the crosslinking reaction, care must be taken to ensure that,
during the coating operation, the crosslinking process has not
progressed too far, since this alters the coating characteristics
of the formulation. Particular preference is given in this case to
producing a compound which already comprises filler particles of
kind B and polymers of kind A, but with the groups X which
originates from group Z by a chemical reaction, dissociation or
decomposition by means of electrochemical radiation, particulate
radiation, sound energy or, most advantageously, thermal energy,
and Y selected such that they are able to react not directly with
one another but rather only through the intermediacy of a
crosslinker or a coupling reagent. In that case, crosslinkers or
coupling reagents are preferably metered into the otherwise fully
homogenized compound immediately prior to the coating operation,
and are mixed with said compound. Optionally, a two-component or
multicomponent operation is conducted in which the particularly
advantageous aspect of this invention lies in the fact that because
of the protection and/or blocking of group X, in this process, all
of the raw materials must be divided up between at least two mass
reservoirs in such a way as to ensure the physical separation, up
until immediately prior to the coating operation, of all those raw
materials that are capable of a reaction with one another. In the
case of a thermal conversion or deprotection of the group Z to form
the group X, it is of advantage, during the compounding, to set a
temperature profile, so that the temperature needed for the
conversion or deprotection, which with particular preference is
much higher than the standard operating temperatures, is achieved
only shortly before the removal of the adhesive from the kneader,
for example, in the case of a batch process, or only shortly before
exit from the compounding assembly in the case of a continuous
process, in order to prevent excessive crosslinking in the course
of mixing. The thermal energy for the crosslinking reaction is then
either taken from the preheated flows of composition, made
available by setting a temperature of the coating assembly, or
realized by way of a heating tunnel and/or an infrared section
after the coating. It is likewise possible in accordance with the
invention to utilize the thermal energy given off in one or more
exothermic reactions in order for this thermal reaction to proceed.
Combinations of these process possibilities particularly with the
radiation crosslinking processes are possible within the context of
this invention. Where the conversion or deprotection of the group Z
to form the group X takes place by means of electromagnetic
radiation, particulate radiation and/or sound energy, it is
particularly advantageous, in the case both of a continuous
operating regime and of a batch operating regime, to allow the
irradiation or sonication of the adhesive to take place between the
compounding operation and the coating operation, and this can be
done with the methods already described above and also with the
apparatus for generating the radiation or ultrasound, respectively.
In both advantageous embodiments of the invention the thermal
energy for the crosslinking reaction is then either taken from the
preheated flows of composition, made available by setting a
temperature of the coating assembly, or realized by way of a
heating tunnel and/or an infrared section after the coating
operation. It is likewise possible in accordance with the invention
to utilize the thermal energy given off in one or more exothermic
reactions in order for this thermal reaction to proceed.
[0141] With great preference in the context of this invention,
self-adhesive products of the invention are produced in a
continuous operation in the course of which the steps of
compounding, of coating, of crosslinking and, where appropriate, of
drying are coupled directly and hence in which an inline operation
is employed, it also being possible for individual process steps to
run at least partially simultaneously, such as, for example,
crosslinking and drying.
Self-Adhesive Products
Product Constructions
[0142] The pressure-sensitive adhesives prepared by the processes
of the invention can be utilized for constructing different kinds
of self-adhesive products such as, for example, self-adhesive tapes
or self-adhesive sheets. Inventive constructions of self-adhesive
products are depicted in FIG. 7. Each layer in the self-adhesive
tape constructions of the invention may, as an alternative, be in
foamed form.
[0143] In the simplest case a self-adhesive product of the
invention is composed of the pressure-sensitive adhesive (PSA) in
single-layer construction (construction in FIG. 7.1). This
construction may optionally be lined on one or both sides with a
release liner, e.g., a release film or release paper. The layer
thickness of the PSA is typically between 1 .mu.m and 2000 .mu.m,
preferably between 5 .mu.m and 1000 .mu.m.
[0144] The PSA may additionally be on a backing, in particular a
film or paper backing or a sheetlike textile structure
(construction in FIG. 7.2). The backing in this case may have been
pretreated in accordance with the prior art on the side facing the
PSA, so that, for example, an improvement in PSA anchorage is
obtained. The side may also have been provided with a functional
layer which can act, for example, as a barrier layer. The reverse
of the backing may have been pretreated in accordance with the
prior art so as to achieve, for example, a release effect. The
reverse of the backing may also have been printed. The PSA may
optionally be lined with a release paper or release film. The PSA
has a typical layer thickness of between 1 .mu.m and 2000 .mu.m,
preferably between 5 .mu.m and 1000 .mu.m.
[0145] In the case of the construction according to FIG. 7.3 the
self-adhesive product is a double-sided product comprising as its
middle layer, for example, a backing film, a backing paper, a
sheetlike textile structure or a backing foam. In this
construction, PSAs of the invention of identical or different kind
and/or of identical or different layer thickness are employed as
top and bottom layers. The backing (or carrier) may in this case
have been pretreated in accordance with the prior art on one or
both sides, thereby achieving, for example, an improvement in PSA
anchorage. It is also possible for one or both sides to have been
provided with a functional layer which connect, for example, as a
barrier layer. The PSA layers may optionally be lined with release
papers or release films. The layers of PSA typically have
thicknesses, independently of one another, of between 1 .mu.m and
2000 .mu.m, preferably between 5 .mu.m and 1000 .mu.m.
[0146] As a further double-sided self-adhesive product, the
construction according to FIG. 7.4 is an inventive variant. A PSA
layer of the invention carries on one side a further PSA layer
which, however, may be of any desired nature and therefore need not
be inventive. The construction of this self-adhesive product may be
lined optionally with one or two release films or release papers.
The layers of PSA typically have thicknesses, independently of one
another, of typically between 1 .mu.m and 2000 .mu.m, preferably
between 5 .mu.m and 1000 .mu.m.
[0147] As in the case of the construction in FIG. 7.4, the
construction according to FIG. 7.5 is a double-sided self-adhesive
product which comprises a PSA of the invention and also one other
PSA of any kind. In FIG. 7.5, however, two PSA layers are separated
from one another by a backing (or carrier), a backing film, backing
paper, a sheetlike textile structure or a backing foam. The backing
in this case may have been pretreated in accordance with the prior
art on one or both sides, thereby achieving, for example, an
improvement in PSA anchorage. It is also possible for one or both
sides to have been provided with a functional layer which connect,
for example, as a barrier layer. The PSA layers may optionally be
lined with release paper or release film. The PSA layers have
thicknesses, independently of one another, of typically between 1
.mu.m and 2000 .mu.m, preferably between 5 .mu.m and 1000
.mu.m.
[0148] The self-adhesive product of the invention according to FIG.
7.6 comprises a layer of inventive material as a middle layer,
which is provided on both sides with any desired PSAs of identical
or different type. One or both sides of the middle layer may have
been provided with a functional layer which connect, for example,
as a barrier layer. For the outer PSA layers it is not necessary
for inventive PSAs to be employed. The outer PSA layers may
optionally be lined with release paper or release film. The outer
PSA layers have thicknesses, independently of one another, of
typically between 1 .mu.m and 2000 .mu.m, preferably between 5
.mu.m and 1000 .mu.m. The thickness of the middle layer is
typically between 1 .mu.m and 2000 .mu.m, preferably between 5
.mu.m and 1000 .mu.m.
Test Methods
[0149] In the description of this invention, numerical values are
given for systems of the invention and reference is made to test
methods by means of which such data can be determined. These test
methods are collated below.
Determining the Gel Fraction (Test A)
[0150] Coated and crosslinked, solvent-free PSA samples are welded
into a nonwoven polyethylene pouch. Soluble constituents are
extracted with toluene for a period of three days, the solvent
being replaced daily. The difference in sample weights before and
after extraction gives the gel index, as the percentage weight
fraction of the polymer which cannot be extracted with toluene.
Determining the Bond Strength (Test B)
[0151] The peel strength (bond strength) is tested in accordance
with PSTC-1. A PSA layer 50 .mu.m thick is applied to a PET film 25
.mu.m thick. A strip of this specimen 2 cm wide is adhered to a
sanded steel plate by rolling over the specimen back and forth five
times using a 5 kg roller. The plate is clamped in and the
self-adhesive strip is pulled off from its free end on a tensile
testing machine at a peel angle of 180.degree. and a speed of 300
mm/min.
Determining the Holding Power (Test C)
[0152] The test takes place in accordance with PSTC-7. A PSA layer
50 .mu.m thick is applied to a PET film 25 .mu.m thick. A strip of
this specimen 1.3 cm wide is adhered to a polished steel plaque
over a length of 2 cm using a 2 kg roller, the specimen being
rolled over back and forth twice. The plaques are equilibrated
under test conditions (temperature and atmospheric humidity) for 30
minutes, but without a load. Then the test weight is hung on,
thereby producing a shearing stress parallel to the surface of the
bond, and a measurement is made of the time taken for the bond to
fail.
Microshear Test (Test D)
[0153] This test serves for accelerated testing of the shear
strength of adhesive tapes under temperature load.
Sample Preparation for Microshear Test:
[0154] An adhesive tape (length approximately 50 mm, width 10 mm)
cut from the respective sample specimen is adhered to a steel test
plate, which had been cleaned with acetone, such that the steel
plate protrudes beyond the adhesive tape to the right and left, and
the adhesive tape protrudes beyond the test plate by 2 mm at the
top edge. The bond area of the sample in terms of
height.times.width is 13 mm.times.10 mm. The bond site is
subsequently rolled over six times using a 2 kg steel roller at a
speed of 10 m/min. The adhesive tape is reinforced flush with a
stable adhesive strip which serves as a support for the travel
sensor. The sample is suspended vertically by means of the test
plate.
Microshear Test:
[0155] The sample specimen for measurement is loaded at the bottom
end with a weight of 100 g. The test temperature is 40.degree. C.,
the test duration 30 minutes (15 minutes' loading and 15 minutes'
unloading). The shear travel after the predetermined test duration
at constant temperature is reported as the result in .mu.m, as both
the maximum value ["max"; maximum shear travel as a result of
15-minute loading] and as the minimum value ["min"; shear travel
("residual deflection") 15 min after unloading; on unloading there
is a backward movement as a result of relaxation]. Likewise
reported is the elastic component in percent ["elast"; elastic
component=(max-min)*100/max].
SAFT--Shear Adhesive Failure Temperature (Test E)
[0156] The SAFT test is an accelerated test of the short-term
temperature resistance of the adhesives or adhesive tapes. The
specimens were reinforced with a 50 .mu.m aluminium foil and the
remaining adhesive side was adhered to a ground steel test plate,
which had been cleaned with acetone, and was then rolled over six
times using a 2 kg steel roller at a speed of 10 m/min. The bond
area of the sample in terms of height.times.width was 13
mm.times.10 mm. The top part of the specimen, which protrudes by 2
mm beyond the test plate, was reinforced with a stable adhesive
strip. At that point, after the sample had been vertically
suspended, the travel sensor was mounted. The sample under
measurement was loaded at the bottom end with a weight of 50 g.
Then, beginning at 25.degree. C., the steel test plate with the
bonded sample was heated, at a rate of 9.degree. C. per minute, to
the final temperature of 200.degree. C. Using the travel sensor, a
measurement was made of the slip travel of the sample as a function
of temperature and time. Measurement was ended when the intended
final temperature was reached or when a slip travel of >1000
.mu.m had been attained.
[0157] The SAFT test is able to supply two test features: SAFT
shear travel or SAFT short-term temperature resistance. The SAFT
shear travel is the slip travel in .mu.m when the final temperature
is reached. The SAFT short-term temperature resistance is the
temperature at which a slip travel of 1000 .mu.m is attained. The
value reported is in each case the average from a duplicate
determination.
TABLE-US-00001 TABLE 1 Functional Conversion into the groups of
type X groups of type Z --NCO --CNR.sup.aR.sup.b
--CR.sup.aR.sup.6--N (nitrene) --CO.sub.2H R--SH R--OH
--CR.sup.aR.sup.b (radical) --NHCO.sub.2R.sup.1 X X
--NH(C.dbd.O)NR.sup.1R.sup.2 X X --SO.sub.2N.sub.3 X
--CO.sub.2C(CH.sub.3).sub.3 X R--S(C.dbd.O)CH.sub.3 X ##STR00003##
X --Pl X
TABLE-US-00002 TABLE 2 Functional groups Functional groups of type
Y of type X --CR.sup.a.dbd.CR.sup.bR.sup.c
--OC(.dbd.O)CR.sup.d.dbd.CR.sup.aR.sup.b
--OCR.sup.a.dbd.CR.sup.bR.sup.c ##STR00004## --NCO
--NR.sup.aR.sup.b --N.sub.3 --CR.sup.1.dbd.CR.sup.2R.sup.3 X X X X
X --OC(.dbd.O)CR.sup.4.dbd.CR.sup.1R.sup.2 X X X X X
--OCR.sup.1.dbd.CR.sup.2R.sup.3 X X X X ##STR00005## X X X --NCO X
X X --NR.sup.1R.sup.2 X X X X --N.sub.3 X X X --OH X X --SH X X X
--C(.dbd.O)R.sup.1 X --CO.sub.2H X X X
--C(.dbd.O)--O--C(.dbd.O)R.sup.1 X Cyclic acid anhydride X
--CR.sup.1R.sup.2 (radical) X X X X --C.ident.CR.sup.1 X
--CR.sup.1R.sup.2--N (nitrene) X X X --CR.sup.5R.sup.6H X X X
Functional groups Functional groups of type Y of type X --OH --SH
--C(.dbd.O)R.sup.a --CO.sub.2H --C(.dbd.O)--O--C(.dbd.O)R.sup.a
Cyclic acid anhydride --CR.sup.aR.sup.b (radical)
--CR.sup.1.dbd.CR.sup.2R.sup.3 X X
--OC(.dbd.O)CR.sup.4.dbd.CR.sup.1R.sup.2 X
--OCR.sup.1.dbd.CR.sup.2R.sup.3 X ##STR00006## X X X X --NCO X X X
--NR.sup.1R.sup.2 X X X X --N.sub.3 --OH X X X --SH X X X X
--C(.dbd.O)R.sup.1 X --CO.sub.2H X X X
--C(.dbd.O)--O--C(.dbd.O)R.sup.1 X X X Cyclic acid anhydride X X X
--CR.sup.1R.sup.2 (radical) --C.ident.CR.sup.1 X
--CR.sup.1R.sup.2--N (nitrene) --CR.sup.5R.sup.6H X Functional
groups Functional groups of type Y of type X --C.ident.CR.sup.a
--CR.sup.aR.sup.b--N (nitrene) --CR.sup.eR.sup.fH
--CR.sup.1.dbd.CR.sup.2R.sup.3 X
--OC(.dbd.O)CR.sup.4.dbd.CR.sup.1R.sup.2 X
--OCR.sup.1.dbd.CR.sup.2R.sup.3 X ##STR00007## --NCO
--NR.sup.1R.sup.2 --N.sub.3 X --OH --SH --C(.dbd.O)R.sup.1
--CO.sub.2H --C(.dbd.O)--O--C(.dbd.O)R.sup.1 Cyclic acid anhydride
--CR.sup.1R.sup.2 (radical) X X --C.ident.CR.sup.1
--CR.sup.1R.sup.2--N (nitrene) X X --CR.sup.5R.sup.6H
EXAMPLES
Example 1
Preparation of N-(triethoxysilylpropyl)glycine Benzoin Ester
(benzoin acrylate-aminosilane adduct)
[0158] 22.1 g (0.1 mol) of .gamma.-aminopropyltriethoxysilane
(Dynasylan.RTM. AMEO, Degussa AG) were charged to a 250 ml
three-necked brown glass flask. Subsequently 26.6 g (0.1 mol) of
benzoin acrylate in 80 ml of THF were added slowly from a dropping
funnel to the AMEO solution, care being taken to ensure that the
internal temperature did not climb above 30.degree. C. The solution
was cooled with a water bath. The solution was stirred at room
temperature for 20 hours and then the solvent was removed under
reduced pressure, giving 58.9 g of an amber-coloured oil.
NMR-spectroscopic analysis of the crude product showed that the
desired product was present with a purity of >90%.
Process 1: Surface Modification of the Fillers
[0159] The surface modification took place in a method based on F.
Bauer, H. Ernst, U. Decker, M. Findeisen, H. J. Glasel, H.
Langguth, E. Hartmann, R. Mehnert, C. Peuker, Macromol. Chem. Phys.
2000, 201, 2654-2659.
[0160] Fillers present in the form of solids must first be
dispersed in isopropanol or acetone. For this purpose, two
different dispersion methods were employed. One was the
rotor-stator method using an Ultra-Turrax.RTM. T 25 basic from
IKA-Werke GmbH & Co. KG, Germany, and the other was
ultrasonication of the particles using the UP200S ultrasound
processor from Hielscher, Germany, with different sonotrode
geometries and a frequency of 1 kHz. The solids content of the
dispersions was 10% to 30% by weight.
[0161] The functionalized silane was added with vigorous stirring
to the dispersion of filler in a one-necked flask with reflux
condenser (0.2-0.6 mmol of silane per gram of filler). Subsequently
a 0.1 M solution of maleic acid in water (0.2 mL per gram of
filler) was added slowly dropwise and the reaction mixture was
stirred at 60.degree. C. for four hours. The dispersion is stable
for about four days and can be processed without further working
up. However, it is likewise possible to remove the continuous phase
under reduced pressure and to carry out further processing of the
resultant solid, after drying, as a crosslinker.
Process 2: Preparation of the Modified, Acrylate-Based Hotmelt
PSAs
[0162] The acrylate hotmelt PSAs were melted in a feed extruder
(single-screw conveying extruder from Troester GmbH & Co. KG,
Germany) and conveyed with this extruder, in the form of a polymer
melt, directly into a Welding twin-screw extruder (Welding
Engineers, Orlando, USA; model 30 MM DWD; screw diameter 30 mm,
length of screw 1=1258 mm; length of screw 2=1081 mm; 3 zones). Via
a solids metering system, the resin Dertophene.RTM. T110 (DRT
Resines, France, terpene-phenolic-based tackifier resin, softening
point 110.degree. C., hydroxyl value 45-60) was metered in zone 1
and mixed in homogeneously. The parameters are given here by way of
example for resin compounding with a base polymer consisting of
ethylhexyl acrylate, butyl acrylate, methyl acrylate,
2-hydroxyethyl methacrylate (HEMA), and acrylic acid
(43.5:43.5:8:2:3). Rotary speed was 451 rpm, the motor current 42
A, and a throughput of 30.1 kg/h was realized. The temperatures in
zones 1 and 2 were each 105.degree. C., the melt temperature in
zone 1 was 117.degree. C., and the temperature of the composition
on exit (zone 3) was 100.degree. C.
Process 3: Preparation of the Modified PSAs in Solution and
Laboratory Specimens
[0163] A polymer solution with a solids content between 40% and 60%
by weight was admixed with the respective amounts of resins, ageing
agents, modified fillers (in the form of a dispersion in the
present case) and, if necessary, additional crosslinking reagents,
and the mixture was homogenized on a roller bed for 12 hours. In
some cases further amounts of solvent were added as well, in order
to set a viscosity suitable for the drawdowns. Subsequently the
mixture was drawn down with a doctor blade onto a carrier (film,
paper, nonwoven) with a defined coat weight (weight per unit area),
and the laboratory specimen was dried in a drying cabinet at an
elevated temperature.
Process 4: Preparation of the Inventive Adhesive Tapes, Blending
with the Functionalized Particles Serving as Crosslinkers, and
Coating
[0164] The acrylate hotmelt adhesives produced by process 2 were
melted in a feed extruder (single-screw conveying extruder from
Troester GmbH & Co. KG, Germany) and, using this extruder, were
conveyed in the form of a polymer melt into a twin-screw extruder
(Leistritz, Germany, ref. LSM 30/34). The assembly is heated
electrically from the outside and air-cooled by a number of fans,
and is designed such that, with effective distribution of the
particles and of the coupling reagents that are additionally
required in certain cases, in the polymer matrix, a short residence
time of the adhesive in the extruder is ensured at the same time.
For this purpose the mixing screws of the twin-screw extruder are
arranged in such a way that conveying elements alternate with
mixing elements. The respective filler particles, particle
dispersions, and coupling reagents are added with suitable metering
equipment, at a number of points if appropriate (FIG. 8: metering
points 1.1 and 1.2; additionally: 1.3=twin-screw extruder, BW=web
roll; RW=doctor roll of a two-roll applicator unit; the latter here
is shown only by way of example and without restriction (and, where
appropriate, using metering assistants, into the unpressurized
conveying zones of the twin-screw extruder.
[0165] Following emergence of the compounded adhesive, i.e., the
adhesive blended with the particles and the coupling reagents
required additionally in some cases, from the twin-screw extruder
(outlet: annular die, 5 mm in diameter), coating takes place onto a
carrier material in web form, in accordance with FIG. 8. The time
between the metered addition of the particles surface-modified with
crosslinkers to the point of shaping or coating is denoted the
processing time. The processing time indicates the period in which
the adhesive blended with the particles can be coated with a
visually good appearance (gel-free, speck-free). Coating takes
place with web speeds between 1 m/min and 20 m/min; the doctor roll
(RW) of the two-roll applicator unit is not driven.
Examples 2-5
Carbamate-Functionalized Particles
[0166] Using Process 1, two silica particle types with different
morphologies were functionalized, both of which were already in
dispersion in isopropanol (Aerosil.RTM. VP Disp LE 7520 from
Degussa AG (fumed silica), diameter: 70 nm, 20% by weight in
isopropanol, fractal geometry; Highlink.RTM. NanoG from Clariant
(precipitated silica), diameter: 13 nm, 30% by weight in
isopropanol, spherical particles). To modify the surface,
3-triethoxysilylpropyl tert-butylcarbamate from Gelest Inc., USA
and N-(trimethoxysilylmethyl) O-methylcarbamate (Geniosil.RTM. XL
63, Wacker-Chemie GmbH) were used.
TABLE-US-00003 TABLE 3 Particle diameters measured by means of
dynamic light scattering. Particle diameter Particle diameter
unmodified modified Silane Silica [nm] [nm] tert- Aerosil .RTM. VP
70 143 Butylcarbamate Disp LE 7520 tert- Highlink .RTM. 13 33
Butylcarbamate NanoG Ethylcarbamate Aerosil .RTM. VP 70 140 Disp LE
7520 Ethylcarbamate Highlink .RTM. 13 34 NanoG
[0167] 100 g of a polyacrylate consisting of ethylhexyl acrylate,
butyl acrylate, methyl acrylate, 2-hydroxyethyl acrylate and
acrylic acid (43.5:43.5:8:2:3) with a glass transition temperature
T.sub.g of -31.2.degree. C. and 30 g of the terpene-phenolic resin
Dertophene.RTM. DT 110 (DRT Resines, France) were dissolved in 80
mL of 1:1 mixture of benzene/acetone, after which the modified
particles in the form of a dispersion were added (1%, 2.5%, 5%, and
10% by weight, based on polymer), and the mixture was homogenized
(process 3). The adhesive was applied with a coat weight of 50
g/m.sup.2 to an etched PET film 23 .mu.m thick (from Laufenberg
GmbH) and dried for 10 minutes at 120.degree. C. or 180.degree.
C.
TABLE-US-00004 TABLE 4 Technical adhesive data. Pure 2.5% com- 1%
by by 5% by 10% by Measurement Silica Silane position weight weight
weight weight Bond strength, steel [N/cm] Drying at 180.degree. C.
Aerosil .RTM. tert- 8.23 7.88 6.99 6.75 6.01 VP Disp Butylcarbamate
LE 7520 Ethylcarbamate 8.24 8.09 7.54 6.82 6.03 Highlink .RTM.
tert- 8.18 7.01 7.21 6.96 6.14 NanoG Butylcarbamate Ethylcarbamate
8.20 7.95 8.03 7.05 7.03 Holding power RT (70.degree. C.) [min]
Drying at 120.degree. C. Aerosil .RTM. Ethylcarbamate 16 (0) 24 (0)
26 (0) 32 (0) 58 (0) VP Disp LE 7520 Highlink .RTM. Ethylcarbamate
16 (0) 22 (0) 23 (0) 24 (0) 57 (0) NanoG Drying at 180.degree. C.
Aerosil .RTM. Ethylcarbamate 17 (0) 702 (5) 10 000 (1466) 10 000
(10 000) 10 000 (10 000) VP Disp LE 7520 Highlink .RTM.
Ethylcarbamate 16 (0) 4758 (41) 9712 (302) 10 000 (480) 10 000
(238) NanoG Microshear travel [.mu.m] Drying at 180.degree. C.
Aerosil .RTM. Ethylcarbamate 433 386 207 72 32 VP Disp LE 7520
Highlink .RTM. Ethylcarbamate 433 297 267 112 101 NanoG
Example 6
Particles with Deactivated Phenol Modification
[0168] Using process 1, the silica particles from Degussa AG
(Aerosil.RTM. VP Disp LE 7520) were modified with
2-hydroxy-4-(3-triethoxysilylpropoxy)diphenyl ketone from Gelest
Inc. Using process 2, the base polymer described therein was mixed
with the Dertophene.RTM. DT 110 resin and then processed further by
process 4. First of all the particles and then a trifunctional,
isocyanate-based crosslinker (Desmodur XP 2410, Bayer Material
Science) were metered in and the melt mixture was homogenized at
120.degree. C. The adhesive was applied with a coat weight of 50
g/m.sup.2 to an etched PET film 23 .mu.m thick (from Laufenberg
GmbH).
TABLE-US-00005 TABLE 5 Technical adhesive data. 5% by weight 5% by
weight 0.3% by unmodified modified weight Aerosil .RTM. VP Disp LE
Aerosil .RTM. VP Disp LE Pure Desmodur 7520, 0.3% by weight 7520,
0.3% by weight Measurement composition XP 2410 Desmodur XP 2410
Desmodur XP 2410 Bond 8.25 7.37 6.70 6.79 strength, steel [N/cm]
Holding power 16 10 000 10 000 10 000 RT [min] Holding power 0 141
93 10 000 70.degree. C. [min] Microshear 1277 115 164 66 travel
[.mu.m]
Example 7
Crosslinking of Natural Rubber with Sulfonazide-Modified
Particles
[0169] Using process 1, the Aerosil.RTM. VP Disp LE 7520 silica
particles from Degussa AG were modified with
6-azidosulfonylhexyltriethoxysilane from Gelest Inc. Subsequently
55.4 g of Kautschuk TSR Natur (Natural TSR Rubber, Eastman Chemical
Company), 5.9 g of Staybelite Resin E (Eastman Chemical Company),
5.3 g of Dymerex (Eastman Chemical Company), 32.7 g of Dercolyte S
115 (DRT Resines, France), and 0.6 g of Irganox 1520 (Ciba
Speciality Chemicals) and 1%, 5% and 10% by weight of the modified
silica particles, based on the rubber, were mixed by process 3 with
127 g of toluene and the mixture was homogenized on a roller bed
for a period of 12 hours. The adhesive mixture was applied with a
coat weight of 45 g/m.sup.2 to crepe paper, which was subsequently
dried at 140.degree. C. for 15 minutes to allow the formation of
the nitrene as a reactive intermediate. The further reaction can
also be carried out at room temperature.
TABLE-US-00006 TABLE 6 Technical adhesive data Filler Bond
Microshear Elastic content strength Holding power travel component
[%] [N/cm] [min] 500 g [.mu.m] [%] SAFT 0 2.89 121 1350 8.9
132.degree. C. 1 2.94 207 525 10.5 150.degree. C. 5 2.83 4515 200
32.5 201.degree. C. 10 2.18 10 000 148 24.3 198 .mu.m
Examples 8-9
Crosslinking of SIS and SBS with Sulfonazide-Modified Particles
[0170] By process 1, the elongated silica particles
Organosilicasol.TM. IPA-ST-UP from Nissan Chemical America
Corporation (diameter: 10-15 nm, length: 40-100 nm, 31% by weight
in isopropanol) were modified with
6-azidosulfonylhexyltriethoxysilane from Gelest Inc. Then 1% by
weight of the modified silica particles, based on the synthetic
rubber, and the SIS adhesive (89 g of Kraton 1165 (Eastman Chemical
Company), 90 g of Dercolyte S 115 (DRT Resines, France), 20 g of
Wingtack 10 (Sartomer), and 1 g of Irganox 1010 (Ciba Speciality
Chemicals)) or the SBS adhesive (69 g of Kraton D 1102 (Eastman
Chemical Company), 209 of Kraton D1118 (Eastman Chemical Company),
909 of Dercolyte S 115 (DRT Resines, France), 20 g of Wingtack 10
(Sartomer), and 19 of Irganox 1010 (Ciba Speciality Chemicals))
were mixed by process 3 with 216 g of benzine, 54 g of acetone, and
30 g of toluene, and the mixture was homogenized on a roller bed
for a period of 12 hours. The adhesive mixture was applied with a
coat weight of 50 g/m.sup.2 to an etched PET film 23 .mu.m thick
(from Laufenberg GmbH) which was subsequently dried at 140.degree.
C. for 15 minutes to allow the formation of the nitrene as a
reactive intermediate. The further reaction can also be carried out
at room temperature.
TABLE-US-00007 TABLE 7 Technical adhesive data. Filler Bond Holding
Microshear Elastic content strength power 40.degree. C. travel 1 kg
component [%] [N/cm] [min] [.mu.m] [%] SAFT SIS composition 0 9.93
5682 215 89.6 115.degree. C. 1 11.50 10 000 109 92.6 135.degree. C.
SBS composition 0 12.24 6980 123 76.5 117.degree. C. 1 7.99 10 000
85 87.8 127.degree. C.
* * * * *